There are several situations in Emergency Medicine when it is desirable to promote a prompt diuresis to fill the bladder or obtain urine for diagnostic tests. We attempted to determine which of 3 commonly used intravenous solutions is most effective in establishing urine flow. In a prospective, randomized double-blind crossover study of 12 healthy male volunteers, we rapidly infused 20 cc/kg of D5W, D51/2NS, or 1/2NS immediately after voiding. Voided urine volumes were then recorded at 30, 60, 90, and 120 min postinfusion and the degree of glycosuria, if any, was noted. Total mean urine volume after D5W was 1181 ml, significantly greater than after 1/2NS (825 ml) and 1/2NS (630 ml), which did not differ between each other. Mean urine volume was greater at every time interval for the D5W group, and glycosuria was common in both D5-containing groups. We conclude that in healthy subjects, D5W is more effective in promoting rapid diuresis than are sodium-containing solutions.