Not long before the release of CODE: Veronica, images circulated around the internet of a boxart for Biohazard 4 for the PlayStation 2. A close investigation of the box proved it to be fake, but the game itself turned out to be real. It would be half a decade and a wave of non-sequels and side stories before we ever saw the title, however. 

The first build was never made public, but Shinji Mikami revealed that the first version of Biohazard 4 was aiming for a new gameplay style. The build was evidently different enough to create another one of Capcom's most successful games, Devil May Cry. Devil May Cry in and of itself offers hints as to what the final Biohazard 4 eventually became, particularly the inclusion of gothic, European castles in both titles as well as the ending sequences of both games taking place in vehicles with the female co-protagonist in tow as they escape an exploding island.

 

 

In September 2001, Capcom moved the Biohazard series to the GameCube, announcing an unprecedented six titles for one (non-PlayStation) platform: as previously announced, the revisiting of the former Nintendo 64 title, Biohazard 0; a remake of the original Biohazard; a GameCube-exclusive Biohazard 4 (and thus the cancellation of the PlayStation 2 version); and what later turned out to be near-direct ports of Biohazard 2, 3: Last Escape and CODE: Veronica Complete Edition (as opposed to complete remakes as initially reported). This move would have major repercussions on the development of Biohazard 4. 

First, the GameCube announcement signaled that at least five Biohazard games would need to release before Biohazard 4, not taking into account the various PlayStation 2 Gun Survivor and Outbreak incarnations also in development or planning in that period. Things were further complicated by the announcement of the Capcom 5 at the end of 2002, which actually included Biohazard 4 in the line up as well. The lineup's purpose was to showcase unique, but fun and exciting games for the GameCube. This meant that Biohazard 4 would have the lengthiest development cycle to date, and with Production Studio 4 developing several other games, be subject to the influence of the lessons learned from those games (from a development perspective, and a marketing one as well). Biohazard 0 and Biohazard's plot developments would, at least for the initial versions, have an effect on Biohazard 4's plot. 

At the Capcom 5 conference in November 2002, just as Biohazard 0 launched, Capcom showed off the second build of Biohazard 4. Once again, unlike its sequel, the protagonist was instantly recognizable, being Leon S. Kennedy from Biohazard 4, the only one of the four main series protagonists who had yet to be featured in a second game at that point. It showed Leon, wearing a brown jacket making him somewhat reminiscent of Final Fantasy VIII's Squall, invading Umbrella's headquarters, a dark and shadowy location. He is seen being chased by a mysterious swarm, with the trailers mentioned the "Cradle of the Progenitor Virus." Looking back at this trailer, it looks as if many of its ideas and concepts were carried over to Biohazard 5 after being scrapped in this version, as Biohazard 5 features a similar swarm enemy and a plot revolving around said Progenitor Virus.

At E3 2003, Shinji Mikami telecasted a new trailer following his famous "Don't pee your pants!" quote, showing Leon once again, apparently undergoing hallucinations that would be new ground for the series. This time, it shows him in a haunted mansion facing off against a zombie wielding a hook and seemingly possessed dolls in a supernatural environment. It was the first instance we would see the game's over-the-shoulder aiming system. While it was not readily obvious that this trailer was of a different build than the 2002 trailer, Mikami eventually confirmed this to be the case in an interview. Eventually, the assets of this game would be put toward the development of Demento (Haunting Ground), a Clock Tower derivative, which featured a similar environment to this build. People who pre-ordered Biohazard 4 received a Special DVD, which showed a video of a staff member playing through this build.

In January 2004, GameInformer unveiled a vastly new build. Leon was still around, but everything else except for the aiming system was thrown out. This build was eventually what made it to the public, but in typical fashion, some remnants of the earlier builds exist in the final game, albeit subtly so. The castle and various graphical images throughout the game were first seen in the earlier builds. 

All in all, there were four builds of the game: Devil May Cry; November 2002; E3 2003; and the final release. It was a long road to Biohazard 4, for Capcom and for the fans, though it actually did not stop with the January 2005 GameCube release. The PlayStation 2 version, announced in October 2004 and released a year later, included an extra scenario that brought back a subdued but appreciated version of the Biohazard 2 zapping system back to the forefront, and the June 2007 Biohazard 4 Wii Edition proved that Biohazard and the Wii Remote are an excellent mix.