The pharmacokinetics of cefotiam (CTM) was investigated in 7 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). One gram of CTM was infused either intravenously (i.v. group) or intraperitoneally (i.p. group). In the i.v. group, the serum concentration of CTM at 6 hours after infusion was 25.9 mg/L and the half-life value was 5.09 hours, while the peak value of CTM in dialysate was 12.4 mg/L. In the i.p. group without peritonitis, the dialysate concentration of CTM at 6 hours after infusion was 108.6 mg/L. The serum concentration at 15 minutes after infusion was 3.0 mg/L, the corresponding peak value was 14.0 mg/L at 4 and 6 hours after infusion.