The synthesis and microbiological activity of a new series of 5(or 6)-methyl-2-substituted benzoxazoles (IVa-n) and benzimidazoles (Va-h) were described. The in vitro microbiological activity of the compounds was determined against gram-positive, gram-negative bacteria and the yeast Candida albicans in comparison to reference drugs. Microbiological results indicated that the derivatives possessed a broad spectrum of activity against the tested microorganisms and the compounds IVa-g, IVi-k, IVn, Vb-c and Vh showed significant activity against Pseudomonas aeruginosa having MIC values of 25 micrograms/ml, providing higher potencies than the reference drugs tetracycline and streptomycin. Moreover, the derivative 5-methyl-2-(p-chlorobenzyl)benzoazole (IVb) possessed the same potency against Candida albicans as the reference drugs oxiconazole and haloprogin having a MIC value of 6.25 mg/ml. However, none of the derivatives showed a better spectrum of activity than the reference drugs.