The aim of this study was to compare the cytotoxic effects of a newly synthesized thialo benzene derivative 2,4-dithiophenoxy-1-iodo-4-bromobenzene (C18H12S2IBr) and a well-known antifungal agent, fluconazole, in L929 cells. L929 cells were treated with 250, 500, or 1000 mu g/mL of C18H12S2IBr and with the same doses of fluconazole. Cytotoxicity tests including 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl tetrazolium bromide (MTT), lactate dehydrogenase (LDH) leakage, and protein content were compared. Glucose and lactate concentrations were measured to determine alterations in metabolic activity. Apoptosis was investigated by TUNEL test and results were supported with survivin enzyme-linked immunosorbent assay. Treatment with C18H12S2IBr resulted in a concentration-dependent cytotoxicity as indicated by MTT, LDH leakage assay, and decreased protein concentration. The loss of cell viability and the increased LDH leakage in 500 mu g/mL and 1000 mu g/mL C18H12S2IBr and fluconazole groups indicated cell membrane damage and necrotic cell death. In all groups, metabolic activities were altered but apoptosis was not induced. We have previously investigated lower doses of C18H12S2IBr; there was no cytotoxicity in L929 cells. In this study, higher doses caused cytotoxicity and alterations in metabolic activity. When we consider the similar results obtained from fluconazole and especially the lowest dose of C18H12S2IBr, this newly synthesized compound may be a good alternative antifungal agent.