We investigated the clinical efficiency and safety of lamoxactam for treatment of 28 episodes of infection in 26 adult patients (15 males and 11 females) whose ages ranged from 17 to 83 years (mean 48.7). 4 patients had 'ultimately fatal diseases' and the remaining 22 had 'nonfatal diseases'. The clinical condition at the beginning of treatment was 'critical' or 'poor' in 15 cases. Episodes of infection treated were: 14 intraabdominal, 9 bacteremia, 5 nephro-urinary, 3 osteomyelitis, and a miscellaneous group including pneumonia, soft tissue, parameningeal focus and infected V-P shunt. A total of 34 microorganisms were responsible for 25 episodes of infection. 15 and 10 episodes were mono- and polymicrobial, respectively. Isolated microorganisms included 13 aerobic facultative gram-negative bacillus, 5 facultative gram-positive cocci, and 16 anaerobes. Total dosage of lamoxactam administered by patient ranged from 24 to 234 g (mean 57.6 g), and mean duration of therapy was 15.2 days (range 8-42 days). The overall rate of clinical response to lamoxactam was excellent, amounting to 84% of episodes and 91% of patients. Local and general tolerance was good, and lamoxactam had to be discontinued only once during therapy due to an episode of neutropenia. Enterococcal colonization (5 of 26 patients, 19%) and superinfections (3 of 26 cases, 11.5%) were undesirably frequent in our patients. Lamoxactam seems to be an effective and safe single-agent therapy for many bacterial infections. The possibility of enterococcal colonization and superinfections should be monitored, specially in patients with urinary or intraabdominal infections.