New compounds of N-substituted 2-amino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole set were synthesized and tested for their antiproliferative activity as part of our research in the antitumour field. Title compounds were obtained by reaction of sulfinylbis(2,4-dihydroxythiobenzoyl) (STB) with 4-substituted 3-thiosemicarbazides. The structures of compounds were identified from elemental, IR, ¹H-, ¹³C-NMR and MS spectra analyses. The cytotoxicity in vitro against human bladder cancer HCV29T cells was determined. The most active compounds were also tested against human cancer cell lines: SW707 (rectal), A549 (lung) and T47D (breast). The antiproliferative effect of some compounds was higher than cisplatin studied comparatively.