Penicillium citrinum-derived mycotoxin citrinin (CTN) is known to be a toxic agent for humans and animals. Previous studies have shown that CTN leads to toxicity in many biological systems; however, a limited number of studies have been performed to demonstrate the harmful effects of CTN on the male reproductive system. In the present study, the effects of CTN on cytotoxicity and apoptosis were examined in Sertoli cells as a model. Sertoli cells were treated with eight different CTN concentrations (from 0 up to 200 mu M, for 6-72 h). Toxic potential of CTN was estimated by measuring metabolic activity (MTT test), DNA synthesis (BrdU test), and cell membrane damage (LDH test) as well as apoptosis and necrosis (via staining with propidium iodide and Hoechst 33342). The results showed that CTN significantly decreased the cell viability and cell proliferation, increased cytotoxicity, apoptosis, and necrosis in a concentration-dependent manner. Furthermore, CTN showed cytotoxicity in Sertoli cells with an IC50 value of 116.5 mu M for 24 h. In conclusion, these findings clearly showed that, CTN affects Sertoli cells even at low concentrations. Thus, as a result of the damage of CTN shown in Sertoli cells, it can be deduced that CTN may also have detrimental effects on the testes.