Simultaneous use of alternative or complementary medical therapies by cancer patients undergoing conventional medical treatment is extremely common and may not always be disclosed to the patient's treating physician. Cancer patients undergoing Phase I therapy on clinical trials constitute a special population of patients, since by definition, their prescribed therapy is scientifically unproven in terms of efficacy. Phase I patients are closely monitored for adverse effects in order to identify and characterize the toxicities and to define a tolerable dose of their experimental treatment. Thus, the unrecognized use of alternative therapies by patients actively enrolled in phase I trials may potentially confound rational drug development by causing adverse side effects or by contributing to drug interactions. Examples of clinical toxicities induced by alternative medical treatments include liver dysfunction or renal failure caused by herbal preparations, or hematologic abnormalities, such as eosinophilia-myalgia syndrome caused by tryptophan food supplements. Therefore, it is important to document and determine the prevalence of alternative therapy use in this specific patient population; however, this issue has not previously been examined in a scientifically rigorous manner. We propose to conduct a survey and interview study of phase I cancer patients enrolled in ongoing clinical trials at the National Cancer Institute to determine the prevalence of alternative therapy use in this population. This study will also examine patient attitudes and perceptions regarding their use of alternative therapy as compared with their scientifically-sanctioned phase I experimental therapy. This information has important implications for drug development.