A multicenter, double-blind, parallel-group study of 219 patients with pitting edema of various causes was undertaken to determine the efficacy and safety of indapamide, administered orally (PO) in a 2.5-, 5-, or 10-mg once-daily dose, as compared with hydrochlorothiazide, administered PO in a 100-mg once-daily dose. Efficacy was evaluated by determining each patient's weight and degree of pitting edema periodically during 12 weeks of active treatment. Lessening of edema was measured by changes in the depth of pitting in the pretibial area, ten to 14 inches below the patella. The depth of pitting was assigned an arbitrary number between 0 and 4, with 0 equivalent to no edema and 4 equivalent to more than 6 mm of pitting edema. After one week of treatment, the mean reduction of pitting edema from baseline, using the 0 to 4 scale, was 1.6 (30%) in both the indapamide (mean of the three groups) and hydrochlorothiazide groups. There were no significant differences among the three dosage levels of indapamide. After 12 weeks of treatment the mean decrease from baseline was 1.8 (34%), indicating a stable reduction of edema. The mean weight loss at one week was 2.5 kg for the three indapamide groups and 2.6 kg for the hydrochlorothiazide group; this loss was maintained for the 12 weeks of the study. The mean decreases in weight and pitting edema were clinically and statistically significant (P less than 0.05) for both medications.