Antimicrobial activity of bupivacaine and morphine against 10 micrabial strains was studied with an agar dilution method. The strains tested were Escherichia coli (ATCC 25922),Pseudomonas aeruginosa, ATCC 27853),Staphylococcus aureus(ATCC 25923), and one of each of the clinical isolates of Staphylococcus epidermidis (a multiresistant strain),Staphylococcus epidermidis, a sensitive strain),Streptococcus pneumoniae, Streptococcus pyogenes(A),Streptococcus faecalis, Bacillus cereus, andCandida albicans. The antimicrobial effect of bupivacaine was tested at concentrations of 0.5, 1.25, 2.5, and 5 mg/ml (0.05% 0.125%, 0.25%, and 0.5%). Bupivacaine at a concentration of 2.5 mg/ml inhibited the growth of the sensitiveS. epidermidisstrain,S. pyogenes, andS. pneumoniae, and all of the others exceptP. aeruginosaat a concentration of 5 mg/ml. Morphine 0.2 and 2 mg/ml (0.02 and 0.2%) did not inhibit any of the strains.