The safety of L-citrulline was investigated in male and female Sprague-Dawley rats by oral gavage administration for 4 weeks at a dose level of 2,000 mg/kg/day. Animals were sacrificed following the administration period. In the results, there were no toxicologically significant changes in general condition, clinical observations, body weight, food consumption, ophthalmology, urinalysis, hematology, blood chemistry, organ weights, or necropsy. In histopathological evaluation, squamous cell hyperplasia in the limiting ridge in the stomach was observed in some males and females in the test group. However, the lesion was limited and that tissue is specific to rodents. Thus it was considered to be less toxicologically significant. Our results indicate that repeated oral administration with L-citrulline under the present experimental conditions is well tolerated in male and female rats.