SYNOPSIS. The idea of a form-function correlation implies some benefit for the individual that displays it. This is subsumed under the heading of adaptation, the reality of which has recently been questioned. Some caution in the application of adaptationist explanations may be necessary, but the key point is the perceived risk of the extension of adaptationist explanations to the human species. This review documents that adaptation exists and represents the basis for the match of form and function. It stresses that the underlying adaptive mechanisms are much more complex than sometimes assumed. The complexity has led to misunderstanding. Most important, there is no reason to expect perfection or optimization in any simple match. The review concludes with a review of procedures for the study of seemingly adaptive aspects of phenotypes.