c6h6o3: I haven't tried it yet with a pyro neg. Usually I've used it with TMX, which I develop in D-76 (1+1), and which tends not to have enough density range for Azo, but I have read that it works with pyro negs. The effect is actually similar to pyro, since both add density proportionally to the highlights, though selenium intensification doesn't produce the edge effects, etc. of pyro. Try it with a neg that is otherwise a reject and report back!