Antidiarrheal substances interfering with either intestinal motility or intestinal secretion have been used for the management of acute diarrhea. Opiates are the motility inhibitors that appear particularly useful and among these drugs loperamide is the drug of choice due to its low risk of side effects. The question whether antisecretory effects of opiates observed in certain animal experiments is contributory to their antidiarrheal activity in man has not yet been definitely settled. With the exception of chlorpromazine that was felt to be especially useful in cholera, no other antisecretory drug has been used successfully against acute diarrhea. However, future development of new compounds may lead to drugs with potent anti-secretory activity but without unwanted extraintestinal side-effects.