This review summarises the evidence for the potential antineoplastic activity of the staurosporine analogues 7-hydroxystaurospine (UCN-01) and N-benzoylstaurosporine (CGP 41251) and defines the role of the enzyme family protein kinase C (PKC) in the mechanisms by which these agents interfere with malignant cell growth. PKC function is altered in some neoplasias, and this dysfunction has been related to uncontrolled proliferation. PKC also influences resistance of cancer cells against cytotoxic drugs. Staurosporine analogues compete with ATP, even though the exact action by which they inhibit PKC is more complicated. Staurosporine analogues do not exhibit specificity for particular PKC isoenzymes, but they inhibit 'conventional' PKC isoenzymes more potently than 'novel' and 'atypical' ones. They also interfere directly with the cell cycle machinery. Both CGP 41251 and UCN-01 are currently progressing through clinical evaluation. There is a remarkable difference in pharmacokinetic handling of CGP 41251 and UCN-01 between rodents and humans. CGP 41251 and UCN-01 might offer advantages in cancer therapy when applied in combination with conventional cytotoxic agents.