N,N-diethyl-m-toluamide (DEET) is an insect repellent used worldwide, and a common micropollutant in aquatic environments. However, few studies have addressed the molecular mechanism of DEET toxicity and its effects on cell growth and apoptosis. The purpose of this study was to investigate the effect of DEET on the expression of the cell cycle and apoptosis regulatory proteins in human BE(2)-M17 cells. The results showed that DEET significantly decreased the cell viability (40.6 ~ 68.9% of control) at concentrations of 500 ~ 4,000 mg/L. Also, DEET significantly decreased the expressions of CDK 2, CDK 4, and cyclin D1 (3.9 ~ 86.6% of control), at concentrations of 50 ~ 400 mg/L but from 100 mg/L for cyclin E. Furthermore, DEET significantly increased the expression of caspase-3 (223.1 ~ 1,770.6% of control), but significantly decreased Bcl-2 expression (46.1 ~ 86.3% of control) at all concentrations tested. In conclusion, DEET partially affected the expression of CDK/cyclin molecules, but fully affected the expressions of caspase-3 and Bcl-2 in BE(2)-M17 cells.