The minimum inhibitory concentrations (MICs) of three broad-spectrum antibacterial agents used in the therapy of acne were estimated for antibiotic-sensitive and antibiotic-resistant propionibacteria by agar dilution on one-quarter strength Brain Heart Infusion agar. Azelaic acid was the least active of the compounds tested under the conditions used with MICs of 2000–4000μg/ml (10.6–21.3 mM) for both sensitive and resistant strains. The inhibitory activity of benzoyl peroxide and zinc acetate was similar with MICs of 64–128μg/ml (0.26–0.53 mM) for the former and 32–64μg/ml (0.17–0.35 mM) for the latter against all 55 propionibacterial strains tested irrespective of resistance phenotype. These results confirm that all three agents are as active against antibiotic-resistant propionibacteria as against fully sensitive strains. It is recommended that these agents are prescribed either concomitantly with, or immediately following, courses of oral or topical antibiotics for acne in order to minimize the selection and dissemination of antibiotic-resistant strains of propionibacteria.