For many years fans have speculated over how prevalent steroids were at the height of Pride Fighting Championships run as the premier organisation in mixed martial arts. There have been many rumours, and fighters themselves have spoken out about the use of performance enhancing drugs in the Pride era (see this article by the son of Pride and Shooto veteran Chris Brennan).
Seeing it in black and white should put it to bed.
Enson Inoue, Shooto and Pride veteran (and 1-0 in the UFC), posted what is reportedly an excerpt from his Pride contract which isn't ambiguous in the least.
As you can see above, recreational drugs were tested for, but 'performance enhancing stimulants of (the) steroid based family' were 'specifically excluded from the scope of the test'.
In layman's terms, they weren't looking for any steroids. So in theory, a fighter could use them without having to worry about being caught. It doesn't say that steroids are fine and that fighters should use them, but what you see above is about as far away from a deterrent to using performance enhancing drugs as you can find.
Another aspect of Pride was its connections with the Yakuza, and Inoue himself has had to answer allegations of being Yakuza affiliated himself. He spoke about Yakuza involvement, not just Pride, but in all aspects of Japanese business in culture on the Joe Rogan Experience, and I'd recommend watching if you've not looked much into the history of Japanese MMA before.
Another criticism of Pride FC was that the fights were fixed. Gary Goodridge touched on this.
None of this is a revelation to any of us that have witnessed the rise and fall of Japanese MMA, but it's probably the final nail in the coffin in terms of the long running debate as to how much steroids played a part in the fights we continue to discuss to this day.
And despite this, we will probably continue talking about it for some time yet.