This study investigated the disposition and bioavailability of ceftazidime when it was given intraperitoneally. Seven patients were given 1 gm of ceftazidime intravenously, and 1 wk later, the same dose was given intraperitoneally. After both intravenous and intraperitoneal dosing, serum and peritoneal dialysate samples were obtained at set time intervals over a 24-h period. High-performance liquid chromatography was used to determine the ceftazidime concentrations in the serum and dialysate samples. Inspection of the concentration versus time data after intraperitoneal dosing demonstrated that serum ceftazidime concentrations reached therapeutic (> 8 micrograms/mL) levels within 30 min and remained in the therapeutic range for the entire 24-h period. Simulation of a variety of ceftazidime dosing regimens using the mean pharmacokinetic parameters from this population of patients suggests that a regimen of 1.5 gm administered intraperitoneally every 24 h produces trough serum drug concentrations (approximately 40 micrograms/mL) similar to those achieved with a standard regimen of 1.0 gm given intravenously every 24 h in patients undergoing continuous ambulatory peritoneal dialysis. It was concluded that the intraperitoneal dosing of ceftazidime in these patients is an equally effective and a more convenient alternative to its administration.