The combination of amoxicillin and potassium clavulanate will soon be marketed in 2:1 and 4:1 fixed ratio dosage forms. In vitro and in vivo evidence suggests that clavulanic acid, a potent inhibitor of many bacterial beta-lactamase enzymes, will increase the spectrum of amoxicillin to include, at achievable serum concentrations, Haemophilus influenzae, H. ducreyi, Neisseria gonorrhoeae, Staphylococcus aureus and Branhamella catarralis and, at achievable urine levels, many beta-lactamase-producing strains of E. coli, Klebsiella, Proteus and Citrobacter. Both amoxicillin and clavulanic are well absorbed after oral administration, reach peak serum levels in 40-120 min and have similar half-lives of 45 to 90 min. This combination will be suitable for the treatment of complicated urinary tract infections, otitis media, sinusitis and respiratory tract infections. However, precise recommendations for its use will need to await further clinical trials that compare amoxicillin/clavulanate to alternative therapies.