Twenty-four patients were treated with moxalactam for 25 serious infections. Nineteen patients were septicemic and 18 presented severe underlying diseases considered to impair the normal response to bacterial pathogens. All of the pathogens had MICs of less than 12 mg/l except one Pseudomonas aeruginosa strain with an MIC of 32 mg/l. The dosage ranged from 3 to 12 g/day; the route of administration was either i.v. or i.m. The duration of treatment was six to 26 days. Six patients had urinary tract infections (three bacteremia), four had pulmonary abscesses (two bacteremia), five had septic thrombophlebitis (five bacteremia) and ten had miscellaneous infections (nine bacteremia). Twenty-two (92%) patients responded favourably. Four patients (16.6%) developed superinfections due to organisms highly resistant to moxalactam: three Streptococcus faecalis, one Bacteroides fragilis and one Aspergillus flavus. Tolerance was good. Nine moderate adverse reactions were observed: three cases of transient eosinophilia, two of phlebitis, three hepatic enzyme alterations and one rash. Moxalactam kinetics were measured in serum from 15 patients with normal renal function after receiving 1 g i.v. over 30 min. The mean peak level after the infusion was 82.8 +/- 12.1 (SE) mg/l; the mean trough level 8 h later was 6.2 +/- 1.7 (SE) mg/l. The serum half-life was 2.6 +/- 0.6 (SE) h for the beta phase. Plasma clearance was 76.8 +/- 8.2 ml/min. Moxalactam was found to be highly effective in the therapy of life-threatening infections