4-Methylimidazole (4-MEI), a heterocyclic organic chemical compound, is widely found in many foods and consumed by people worldwide. In this research, we aimed to investigate the cytotoxic and genotoxic effects of 4-MEI on human lymphocytes. For this purpose, human peripheral blood lymphocytes were treated with four concentrations of 4-MEI (300, 450, 600 and 750 mu g/ml) for 24 h and 48 h periods and in vitro sister chromatid exchange (SCE), chromosome aberration (CA) and micronucleus (MN) tests were used. 4-MEI induced SCE in human peripheral lymphocytes at three highest concentrations (450, 600 and 750 mu g/ml) in 48 h treatment period. CA and MN were induced in human peripheral lymphocytes at two highest concentrations of 4-MEI (600 and 750 mu g/ml) in 24 h and 48 h treatment periods. The highest concentration of 4-MEI (750 mu g/ml) induced MN formation more than the positive control MMC in 24 h treatment period. In addition, 4-MEI led to a decrease in MI at the highest concentration (750 mu g/ml) in 24h treatment period and at all concentrations in 48 h treatment period. 4-MEI reduced PI at all concentrations in 24 h treatment period and at all concentrations (expect the lowest) for 48 h treatment period. 4-MEI reduced nuclear division index (NDI) at 24 and 48 h treatment periods, even at the highest two concentrations, decreased more than the positive control MMC. Our results showed that 4-MEI pose a genotoxic and cytotoxic effects for human peripheral lymphocytes.