The large number of negative phase III trials in oncology over the last several years has renewed interest in refining phase II oncology clinical trials to maximize the chances of success in phase III testing. More efficient phase II study designs will improve our ability to identify promising agents for testing while accurately identifying nonefficacious agents. Recognizing that new paradigms of phase II trial designs need to be developed, the Clinical Trial Design Task Force of the National Cancer Institute (NCI) Investigational Drug Steering Committee has tackled the question of improving efficiency of phase II clinical trials. In this issue of CCR Focus, four of the major topics discussed are presented. First, the task force recommended that alternate phase II end points should be studied. Second, depending on the characteristics of the specific trial and study population, historical controls or a randomized design may be more appropriate. Third, rational incorporation of biomarkers into phase II trials should be encouraged. Last, novel imaging modalities will be critical in evaluating the clinical benefit of new cytostatic agents.