Amdinocillin is a novel penicillin whose antibacterial activity is derived from its ability to bind specifically and avidly to Penicillin Binding Protein‐2 (PBP 2). Other β‐lactams bind almost exclusively to PBPs 1 and 3. This unique feature has prompted many investigators to predict that amdinocillin would aggressively synergize with other antimicrobials, particularly other β‐lactams. Certain features of these predictions have been realized.Amdinocillin is active alone against many gram‐negative organisms. Pseudomonas and non‐fermenting gram‐negative bacteria, however, are usually resistant. Amdinocillin, in combination with many β‐lactams, exhibits marked synergy against many enterobacteriaceae. No such synergy can be demonstrated for gram‐positive organisms or pseudomonas species. Amdinocillin is not β‐lactamase stable. Organisms which produce high levels of plasma‐mediated β‐lactamase are resistant to the drug.Amdinocillin is widely distributed to most tissues of the body. It is removed by renal tubular secretion which results in prodigious levels of the drug in the urine. Coadministration of probenecid results in markedly elevated plasma levels of amidinocillin and delays its excretion. Amdinocillin has a plasma half‐life of about one hour in patients with grossly normal renal function. Its half‐life increases to 3 to 6 hours in anephric patients. The spectrum of adverse reactions observed with amdinocillin is similar to that of other penicillins.Amdinocillin, as a single agent, is effective in the treatment of urinary tract infections caused by susceptible strains of E. coli and klebsiella and enterobacter species. When amdinocillin is used in concert with other antimicrobials, synergy can frequently be demonstrated but it is essentially limited to gram‐negative aerobic organisms. At present, insufficient data are available to precisely profile the utility of amdinocillin, either alone or in combination, in the