BACKGROUND Traditional herbal formula Gyejibokryeong-hwan (GJBRH; Guizhifuling-wan, Keishibukuryo-gan) consisting five medicinal herbs has been used to treat uterine disorders, gynecological diseases and blood stasis syndrome in Asia. OBJECTIVE We evaluated the safety of GJBRH in Crl:CD Sprague-Dawley (SD) rats over a period of 13 weeks. METHODS To confirm the stability of the components of GJBRH, we analyzed the component contents in GJBRH at different storage periods, using high-performance liquid chromatography. Male and female SD rats were orally administered with GJBRH at doses of 0, 1000, 2000 and 5000 mg/kg/day for 13 weeks and assessed after a 4-week recovery period. Mortality, changes in body weight and food consumption, organ weights, hematology and serum biochemistry were monitored during the experimental period, along with clinical observations, ophthalmological examinations, urinalysis and histopathology. RESULTS There were no significant differences among the eight marker compounds in GJBRH according to storage period. No significant GJBRH-treatment-related toxicological changes were observed in mortality or ophthalmological examinations in either sex. However, soft feces were observed in the male 5000 mg/kg/day group. In addition, there were significant changes in body weight and food consumption in both male and female rats treated with GJBRH at a dose of 5000 mg/kg/day. In the hematological examinations, we found a significant increase in white blood cells, neutrophils and fibrinogen in the 5000 mg/kg/day groups. In the urinalysis, a decrease in the total protein and albumin and an increase in the ovalbumin/globulin ratio were observed in both male and female rats treated with GJBRH at a dose of 5000 mg/kg/day. Histopathological examinations revealed erosion/ulcers and dilated glands in the stomachs of males from the 5000 mg/kg/day group, and squamous cell hyperplasia and epithelial atrophy was observed in the stomachs of both male and female rats treated with GJBRH at a dose of 5000 mg/kg/day. CONCLUSIONS The no-observed-adverse-effect level (NOAEL) was 2000 mg/kg/day for both sexes.