Three Mannich bases: 1-(piperidinomethyl)-2-naphthol(I), 1-(porrylidinomethyl)-2-naphthol(II) and 1-(dimethylaminomethyl)-2-naphthol(III) were synthesized. They were identified by UV, IR, NMR and MS data. In diffusion bioassay, the synthesized bases were evaluated for their antimicrobial activity. Compound (I) showed good activity against Escherichia coli and Pseudomonas aeruginosa at a concentration of 200mgl/ml. Compound (II) exhibited very good activity against the Gram positive strains: Bacillus subtilis and Staphylococcus aureus at a concentration of 200mg/ml, while compound (III) showed good antifungal activity against Aspergillus niger at 200mg/ml.