Three groups of patients with biliary tract disease treated by cholecystectomy were given ceftriaxone. In Group 1 single doses of 150 mg and 1500 mg were given on Days 1 and 5 after cholecystectomy. In Group 2 2 g was given daily for 6 days and the cholecystectomy was on Day 2. Patients in Group 3 received 2 g every 12 h for 3 to 5 doses before cholecystectomy. Plasma samples, urine and T-drain bile were collected at various times from Groups 1 and 2 patients. Gallbladder bile and plasma were collected from Group 3 patients at the time of cholecystectomy. The mean (+/- SEM) T-drain bile-to-plasma concentration ratio of ceftriaxone in Groups 1 and 2 was 6.7 +/- 0.92. The mean (+/- SEM) gallbladder bile-to-plasma concentration ratio was 33 +/- 4.2. No clinically significant differences were detected between the kinetics of ceftriaxone in the cholecystectomy patients compared to normal volunteers. The usual dosage of ceftriaxone appeared adequate for prophylaxis or treatment of biliary tract infection by susceptible organisms.