Hmm ... I may be wrong but I think Michael was talking about White exchanging his light-squared bishop for a black knight.

In general I think it can be quite a good idea - check out the famous Kasparov-Nunn game in the Benoni Slayers section on the main site, in which Bb5xd7 is quite an important part of the attack.

But as sacanode says, there are no hard and fast rules, and it may be that in some positions the exchange favours Black as it relieves some of the cramp in his position and also takes away some of the power of an eventual e4-e5 thrust.

I recently played a very interesting game against the benoni. I used a dynamic line (1.d4 Nf6 2.c4 c5 3.d5 e6 4.Nc3 exd5 5.cxd5 d6 6.e4 g6 7.f4). After an interesting move I played I had the opportunity to exchange my white square bishop with one of my opponent's knight, which I did. I thought that I could exchange one of his knights which are good because of the pawn structure and decrease the pressure in the centre. But in general, in this variation, is it right to exchange this bishop for a knight? Is it preferable to keep this bishop to support the centre? If there is no general rule I can publish the game to give me your opinion as I am still not sure if I made the right decision, even if I got a winning position. Thank you!!!