Genotoxicity of ibuprofen was evaluated by employing the mouse in vivo chromosomal aberration (CA) test. Ibuprofen administered orally at doses of 10, 20, 40, and 60 mg/kg body weight to mice resulted in mitotic depression and induction of CAs. A dose-related decrease in mitotic index (MI) and an increase in the frequencies of chromosomal aberrations per cell (CAs/cell) were recorded in bone marrow cells. However, a statistically significant reduction in MI and an increase in CAs/cell were found for both the higher doses. The results obtained indicate that ibuprofen is capable of inducing dose-dependent genotoxicity in bone marrow cells of mice.