Many common diseases are partly attributable to the genes which an individual inherits. Early steps have now been made in developing ways to determine which genetic variations are important, with some recent successes. This is a collection of papers from the Fifth Annual Molecular Pathology Symposium on the 10 December 1996. They represent the contributions to that meeting made by a set of distinguished scientists and clinicians whose work pertains to the furtherment of our understanding of the genetic components of common diseases and potential future approaches.