Substituted Schiff's bases 2a-o prepared by the treatment of 2-amino-4-(?-methoxyiminocarbomethoxymethyl)-thiazole 1 with different aromatic aldehydes, on cyclocondensation with mercaptoaceticacid and mercaptopropionicacid in dry benzene furnished desired thiazolidinones of type 3a-o and 4a-j, respectively. The structure of the compounds have been assigned on the basis of elemental analyses and spectral data. The products were evaluated for their in vitro growth inhibiting activity against several microbes. Some of the compounds showed significant antitubercular and antifungal activity.