Sulbactam, a beta-lactamase inhibitor, was given as a single agent to 12 subjects with varying degrees of renal dysfunction. The half-life in normal subjects was 1.1 h and increased to 21.3 h in those with terminal renal failure. Sulbactam together with ampicillin was given to a further five subjects. It was concluded that if the two agents are given together, the plasma ratio of one to the other will remain constant whatever the renal function.