Biohazard began opening for local hardcore and thrash bands and gradually built a large following through their outraged sense of injustice, political awareness, and constant touring. Inspired by (but not limited to): Black Sabbath, Iron Maiden, Run DMC, Bad brains, Judas Priest, Cro-Mags, Public Enemy, The Ramones, Agnostic Front, the band set out to create a musical hybrid that would transcend easy categorization and not be bound by limitation. Biohazard was one of the first bands to mix heavy metal and hardcore with elements of hip-hop and rap.

In 1990 they signed their first label at a little record-company which is called Maze Records, Biohazard also released their first LP there, which is published under the name "Biohazard". It sold over 40.000 copies, this bad quantity was based on poor promotion. This album was all about Brooklyn, the gang-wars, drugs, violence, etc. After releasing their debut in 1990, Biohazard set out on their path for world domination. Returning from their first European tour, they realized that the problems they sang about on their first record were not limited to their Brooklyn hometown.

After a long time of fighting about a good record label, Biohazard finally got it's contract with Roadrunner Records. In 1992, the band released the classic URBAN DISCIPLINE, which went on to sell over 1,000,000 copies worldwide. Consequently, Biohazard became support of bigger acts such as House Of Pain, Sick Of It All, Fishbone and Kyuss. Spawning from this record was the video for the track "Punishment" which was the most played video in the history of MTV's Headbanger's Ball and is still regarded as one of the most influential records of the nineties.

In 1993, the hard-core rap group Onyx recorded an alternate version of their hit single "Slam" with Biohazard backing them up. This led to both bands collaborating on the title song for the groundbreaking Judgement Night soundtrack, which sold over 2,000,000 copies in the US. In the same year they changed to Warner Brothers Records Inc. and published their third and most successful studio LP "State Of The World Address". It was produced in winter`94 in Los Angeles with Ed Stasium. In 1994 Biohazard again was touring the entire planet and drawing strength from their loyal fans. SOTWA went on to sell over 1,000,000 copies and spawned the hit single and video "How It Is" featuring Sen-Dog from Cypress Hill. This album was up to now the most controversial Biohazard LP. It criticized the sharp and clear thinking of the band. After this little conflict the Rolling Stone Magazine selected the Biohazard logo for the best logo of the year. The third LP also was the last one for Bobby, who left the band a few times later.

Biohazard went on to release the fourth album called Mata Leao two years later. It was produced for the second time at Warner Brothers with the help of Dave Jerden. Biohazard recorded it with only three members: Evan, Billy, Danny. Without a lead guitarist, but you can hear that it is a great piece of work. The title means, "to kill the lion" and, in a sense, they discovered that their ambitions would lead them to do just that. By facing their fears head on, defeating their inner demons and looking around the globe for answers, the band found the truth inside themselves. Battling drug and alcohol abuse, inter-band strife, record labels folding, merging and abandoning them for more pop flavors, Biohazard staggered like a champion fighter, but never went down. During these difficult years, Biohazard succeeded in sticking it out together. For the Mata Leao Tour in 1996, the band needed a talented lead guitarist, so they choosed the ex-Helmet guitarist Rob Echeverria. With the assistance of Rob they published their first live record "No Holds Barred" in 1997. The whole album was recorded in Hamburg with the helping hands of Roadrunner Records.

After that the band signed to Mercury Records and released the critically acclaimed the fifth record called New World Disorder in 1999. Everything was done again with the help of Ed Stasium, but this time in New York City. In the same year, Biohazard toured for "New World Disorder" among other things in Europe, for example at Rock am Ring / Rock im Park or at the Bizarre festival in Cologne.
Feeling betrayed and misunderstood by their label, the band left Mercury amidst the mass artist genocide that occurred with the merger of Mercury, Island, Def Jam and Polygram into Universal. In 2000, operating on their survival instincts, the band re-grouped and launched a highly successful European/Japan tour with no record label or managerial support. After traveling all over the world, they earned a longer break to began doing the work on the sixth record "Tales From The B-Sides". The LP is full of the coolest b-side and remix shit.

A few month ago, Rob has left the band, he wants to settle down and get married. Fortunately they found a new lead guitarist, his name is Leo Curley. In the meantime Biohazard signed new record deals with SPV/Steamhammer for Europe and Sanctuary for the rest of the world.
During the bands' downtime, the high visibility of being hard-core legends connected Evan with Tom Fontana landing him a high profile starring role portraying the prison convict "Jaz Hoyt" on HBO's critically acclaimed and award winning hit series "OZ".

Billy tried to use his music skills in a trip-hop “massive attackish” project called BLU. The band consists of two members: Billy and a woman Jeni Bair(vocalist). The bands' hard work had earned respect has also brought Billy into the journalism world. Currently working on a collection of "Tales from the Hardside" for later release, you can find some of these tales in magazines like Metal Hammer and FAQ (to name a few) where he has his own monthly column

Danny also undertook some activities outside Biohazard. He joined New York's band called AMONG THIEVES as a replacement for Will Shepler (ex-AGNOSTIC FRONT/MADBALL).

Also during this time, Billy and Danny transformed the bands infamous rehearsal studio/hangout in downtown Brooklyn into a world class digital recording studio now know as Rat Piss Studios. Re-investing into the band, Billy and Danny honed their engineering and productions skills while recording/producing local acts and new Biohazard demos. Armed with a truckload of new music, the band undertook the difficult process of writing, recording and producing their own music. In september of 2001 they released their sixth studio LP (except NHB & Tales From The B-Side) “Uncivilization”. The album features guests the likes of Roger Miret(Agnostic Front), Jamie Jasta of Hatebreed, Phil Anselmo(Pantera), Corey from Slipknot and also mate from Skarhead – Lord Ezec. Unfortunately some months after releasing of “Uncivilization” Biohazard parted ways with Leo Curley. Curley's departure was caused by his desire to write his own material, a prospect which proved virtually impossible in an act that has been composing songs as a three-piece since BIOHAZARD's split with original guitarist Bobby Hambel in the mid-1990s. The split with Leo was mutual, no bad feelings. Biohazard have replaced Leo with former NUCLEUS axeman Carmine Vincent. Vincent is no stranger to the BIOHAZARD camp, having previously traveled with the group as a roadie in addition to having supported BIOHAZARD as the bassist/vocalist for NUCLEUS during a tour of Europe in late 2000. Brand new Biohazard album was recorded with Carmine and entitled "Kill Or Be Killed" (2003) and is the most brutal and heaviest to date.