Abstract This paper reports the results of a survey of 325 out-patients in the hospitals of Kuwait concerning the Moslem practice of fasting during the hours of daylight in the month of Ramadan and the consequences on the drug regimen of patients. More than 60% of patients were found to change the way in which they took their medicines at this time. Particularly in elderly patients this could lead to potentially serious drug interactions and toxic side-effects. The report recommends a greater awareness amongst the prescribers of the problems which can occur in this way, and better counselling of patients so that they understand the potential hazards of non-compliance and the importance of the prescribed regimen for their treatment.