The pharmacokinetics of intravenous ketoprofen were evaluated in 37 patients suffering from acute ureteral colic. Four studies were established to obtain a rapid and persistent analgesic effect: group I: 100 mg of ketoprofen as bolus; group II: short infusion of 100 mg of ketoprofen (1.5 or 2 hours); group III: loading dose of 35 mg ketoprofen plus an infusion of 25 mg/h and 33 mg/h. Serum concentrations of ketoprofen were measured by high pressure liquid chromatography. The mean (+/- SD) values of pharmacokinetic parameters measured with a 2 open compartment model were as follows: distribution half-life: 0.34 +/- 0.19 h; elimination half-life: 2.05 +/- 0.58 h; kel: 0.96 +/- 0.28 h-1; k21: 0.94 +/- 0.42 h-1; k12: 1.00 +/- 0.70 h-1; volume of central compartment: 5.58 +/- 1.67 l; volume of tissue compartment: 5.14 +/- 2.12 l; plasma clearance: 5.10 +/- 1.14 l. h-1. These results concur with previously published data obtained after oral, rectal or intramuscular administration. Ketoprofen due to its peripheric anti-inflammatory, antiprostaglandins and central actions gives the best results with the intravenous administration. Administration of a ketoprofen bolus suppressed pain within ten minutes in 71% of patients.