Artificial neural networks are computer simulations of biological parallel distributed processing systems. They are able to undertake complex pattern recognition tasks, including diagnostic classification, prediction of disease onset and prognosis, and identification of determinants of clinical decisions. These capabilities have been utilized in general medicine, but as yet there has been little application of artificial neural networks in psychiatric research. Artificial neural networks can also be used to create models of brain function, providing a paradigm for cognition and the organization of neural systems that demonstrates how changes at the cellular level can affect information processing. These models are able to encompass both the biological and the behavioral dimensions of psychiatric disorders.