Mannich bases of thymol were synthesized. The aminomethylation reaction was realised in the ortho position of the phenol for compounds 2 (dipropylamine), 3 (benzylamine), and 4 (dibenzylamine) while it was from para position for 1 (dimethylamine), 5 (piperidine), 6 (morpholine) and 7 (N-methylpiperazine). The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory effects of the compounds were asssessed against hCA I and hCA II. All compounds moderately inhibited hCA I and hCA II. The cytotoxicity of the compounds against four human oral squamous cell carcinoma cell lines were compared those against three normal oral cells. Tumor specificity values were about 2 or slightly more for the compounds 2, 3, 4, 5 and 6. Compound 2 showed cytostatic activity against OSCC cell lines at 16 to 32-fold lower concentrations as compared with normal cells. This suggests that compound 2 can be considered as cytotoxicity enhancing drug candidate for further investigations.