A series of novel 5-pyrazoline substituted 4-thiazolidinones have been synthesized. Target compounds were evaluated for their anticancer activity in vitro within DTP NCI protocol. Among the tested compounds, the derivatives 4d and 4f were found to be the most active, which demonstrated certain sensitivity profile toward the leukemia subpanel cell lines with GI₅₀ value ranges of 2.12-4.58 μM (4d) and 1.64-3.20 μM (4f). The screening of antitrypanosomal and antiviral activities of 5-(3-naphthalen-2-yl-5-aryl-4,5-dihydropyrazol-1-yl)-thiazolidine-2,4-diones was carried out with the promising influence of the mentioned compounds on Trypanosoma brucei, but minimal effect on SARS coronavirus and influenza types A and B viruses.