One hundred strains of Campylobacter (44 C. jejuni, 34 C. coli, and 22 C. fetus ssp. fetus) were tested with two new groups of beta-lactams:monobactams (azthreonam and carumonam) and carbapenem (imipenem). MICs were determined by using an agar dilution technique. The monobactams were not effective against Campylobacter species. In contrast, imipenem showed a high activity (MIC 90, 0.25 mg/l). Clinical trials will indicate if this compound can be used in the therapy of severe Campylobacter infections.