The diffusion-collision model of protein folding is assessed. A descri
ption is given of the qualitative aspects and quantitative results of
the diffusion-collision model and their relation to available experime
ntal data. We consider alternative mechanisms for folding and point ou
t their relationship to the diffusion-collision model. We show that th
e diffusion-collision model is supported by a growing body of experime
ntal and theoretical evidence, and we outline future directions for de
veloping the model and its applications.