Behavioural, or psychosocial, oncology refers to the application of the findings and methods of psychology (or more generally the social sciences) to understanding and treating malignant disease. The diagnosis and treatment of cancer are stressful experiences and clinicians can do much to promote adjustment by establishing good rapport, providing appropriate information and by involving patients in management decisions if they wish. Randomized clinical trials of various psychological interventions have shown that a great deal can be done to minimize distress, improve control of various side-effects and enhance quality of life. Although several randomized studies have found that patients who have received a psychological intervention live longer, more studies are urgently needed to confirm this. If survival can be prolonged in this way, it is likely that the underlying psychobiology will vary from one tumour type to another. Attention needs to be directed at how behavioural oncology services should best be delivered within the context of different health services.