Three topical beta-adrenergic blocking agents without preservatives were tested for their ability to inhibit the growth of five microorganisms in vitro. Timolol maleate and befunolol hydrochloride showed no antimicrobial activity; however, bupranolol hydrochloride inhibited microbial growth. The minimum inhibitory concentration of bupranolol hydrochloride was 0.1% for Bacillus subtilis and 0.05% for Staphylococcus aureus and Escherichia coli.