The effects of loperamide oxide 1 mg and 2 mg were compared with placebo and with loperamide 2 mg in 261 patients with acute, nonspecific diarrhea. Time to first relief and time to complete relief of diarrhea were statistically significantly shorter in the three active drug groups than in the placebo group. Compared with placebo, neither dosage of loperamide oxide produced a period of posttreatment constipation. Adverse experiences were (nonsignificantly) less frequent for loperamide oxide 1 mg and 2 mg than for either placebo or loperamide 2 mg. These results suggest that loperamide oxide 1 mg is as efficacious as loperamide 2 mg for the treatment of patients with acute, nonspecific diarrhea. Because of its low potential for causing constipating effects and adverse experiences, loperamide oxide 1 mg may be preferred over either loperamide oxide 2 mg or loperamide 2 mg.