Complementary medicine is fast becoming an integral part of palliative cancer care. There is considerable debate as to whether such treatments require proof of effectiveness through randomized clinical trials or whether it may suffice that patients adopt them with apparent appreciation. We attempt to raise some of the arguments on both sides. The arguments include the logistical problems of conducting research in palliative care, ethical problems of placebo controls, methodological difficulties of standardizing treatments or quantifying subtle effects and the, often considerable, costs of clinical trials. We feel that neither those who argue against nor those who argue in favour of rigorous clinical trials are entirely wrong or entirely right. However, our final verdict is that an absence of rigorous science will critically hinder progress. This, in turn, would be to the detriment of future patients. Through discussing the strengths and weaknesses of both sets of arguments, both sides might learn valuable lessons.