Understanding the dynamics of oncologist-patient communication regarding complementary therapy (CT) use is essential for the development of much-needed clinical guidelines. Discussions of CT use in 314 audio-taped initial consultations between cancer patients and their oncologists were identified and coded. Patients' anxiety levels and coping styles were also assessed. Reference to CT use was found in 91 consultations (29%). Patients and kin initiated most CT discussions, commonly during discussions of patients' medical history, treatment options or prognosis. In half of these discussions, patients volunteered that they were currently using a CT or were considering its use. Discussion of CT use was more likely to occur in consultations with patients who were younger, were better educated, spoke poorer English, had metastatic disease or limited life expectancy and expressed higher levels of fighting spirit and anxious preoccupation and lower levels of fatalism. The most commonly discussed CTs were: changes in diet; use of multivitamins, vitamin C or antioxidants; and having a positive attitude or fighting spirit. The doctor's overall response to CTs was most frequently coded as "encouraging", although 35% of attempts to initiate discussion were ignored by the oncologist. Doctors were more likely to make encouraging statements about CTs typically perceived to be potentially helpful versus potentially harmful. The current findings point to a need for practical consensus on how to communicate with cancer patients on the subject of CT use so that patients can receive the support and guidance that they are seeking from their oncologists.