We have examined the differences in urinary excretion of water, sodium, potassium, chloride, urea, and creatinine produced by different dosage regimens of furosemide in normal volunteers. Three oral dosage regimens were compared: 20 mg daily, 20 mg twice daily, and 40 mg daily, Furosemide, 20 mg, did not produce a significant weight loss, diuresis, or natriuresis in 12 normal subjects. With 40 mg there was a significant weight loss, diuresis, natriuresis, and chloruresis over 24 hr. Comparison of the divided regimen with 40 mg daily revealed significantly greater sodium excretion, and chloride excretion with 20 mg twice daiiy, The divided dosage regimen produced a different pattern of diuresis witn most of the sodium and water excretion occurring after the second dose. These differences in response to different regimens are predictable from pharmacokinetic considerations and may have clinical significance.