For the last decade or more geneticists have been predicting that advances in molecular genetics are going to revolutionize our understanding of psychiatric disorders and human behavior. However, with a few exceptions, these expectations have yet to be fulfilled. As the century draws to a close and we contemplate the prospect of the complete sequence of the human genome it seems timely to consider the state of the field and to consider carefully how it might advance, the problems to be faced and the resources required. Molecular Psychiatry (2000) 5, 22-31.