The pharmacokinetics and pharmacodynamics of furosemide (F) was studied in 8 steroid-responsive nephrotic syndrome (NS) children aged 2.8-6 years with normal renal function and a mean serum albumin concentration of 1.52 +/- (SD) 0.47 g/100 ml. F was given as a single intravenous bolus injection at a dose of 2 mg/kg of actual body weight. The elimination half-life of F calculated from the drug cumulative urinary excretion data was 0.598 +/- 0.24 h. No correlation was found between Ft1/2 and the serum albumin concentration or the age of the patients. The statistically significant diuretic effect of F in the patients lasted 4 h. However, 2 h after F was administered, the children excreted an average of 82.5% of the urine volume collected during significant diuresis. Also, during this time, the patients excreted 57.7% of the given dose of F, which was 96.8% of the drug dose finally excreted in the 24-hour urine collection. This indicates that in some NS children F may be given intravenously more frequently, if necessary, provided that hypovolemia and serum electrolyte depletion resulting from the preceding dose of the drug have been corrected, and the amount of F administered initially was carefully considered.