The ultimate target of pharmacological research is to find new drugs for treating human diseases such as cancer. Agents causing differentiation and thus growth arrest should be particularly useful in this regard. A potential target for such anticancer therapy is the enzyme family protein kinase C (PKC), which is involved in the transduction of signals for cell proliferation, differentiation and apoptosis. Our recent work showing the induction of differentiation in melanoma cells by an activator of one PKC isoform, PKC delta, touches on several important areas of investigation, which will form the basis of this review: the role of individual isoforms of PKC, their downstream targets and their specific substrates, the mechanism of activation of specific Penes involved in the differentiation process, and the molecular basis for the morphological changes associated with differentiation. The central role that PKC plays in these processes points to the need for a greater understanding of the signalling pathways utilized by individual isoforms of this family of enzymes. (C) 1999 Elsevier Science Inc.