Five groups of phenols/naphthols (42 compounds in total) were synthesized and screened against Gram-positive Staphylococcus aureus and Bacillus subtilis, Gram-negative Escherichia coli and Klebsiella pneumoniae, and the fungus Candida albicans. Whereas compounds were found inactive against Gram-negative bacteria, potent activities against Gram-positive bacteria were observed. The activities correlate with the ability of molecules to form quinone methides, suggesting potential new modes of action.KEYWORDS Antimicrobial activity, phenols, naphthols, quinone methides.