The activity of rifampin and other antibiotics against Listeria monocytogenes in vitro and in experimental animal models of listeriosis is reviewed. Rifampin appears to be bacteriostatic against Listeria in vitro, and it is reported to be no more effective than penicillin against experimental listeria meningitis in the rabbit. However, because of insufficient clinical data, the optimal antibiotic regimen for listeriosis in humans remains conjectural. At present, the most frequently recommended regimen is combination therapy with ampicillin and gentamicin; trimethoprim-sulfamethoxazole may prove useful in the penicillin-allergic individual.