Patient preferences and randomised clinical trials.

Allocating patients to different treatments by randomisation in a trial is now accepted almost without question in accounts of trial. Randomisation may reasonably be supposed to play a large part in proposed studies for grant support. The virtue of randomisation is it reduces some types of systematic error that may interfere with the of the results of a trial. Allocating patients to treatments a systematic non-randomised way may introduce bias which destroys. We argue here that despite this advantage random allocation is always suitable. Though patients play an active part in the outcome of treatments, we suggest that clinical trials in which they are required to an effortful and demanding role and those in which they are likely to strong preferences for one treatment need to be considered and conducted.