The synthesis of a series of 2-substituted 3-[2-(1,3,4-thiadiazolyl)]-4-thiazolidinones is described. Evaluation of these derivatives against P 388 lymphocytic leukemia growth in mice revealed that no compound shows significant activity. 2-(2-Thienyl)-3-[2-(1,3,4-thiadiazolyl)]-4-thiazolidinone (I) whose significant activity on P 388 leukemia was reported in a previous paper, was tested against other experimental tumors: it exhibits slight activity also against L 1210 leukemia and M 5076 ascitic sarcoma.