Abstract: AIM: To study the metabolic transformation of Ginsenoside Rg1 (Rg1) given orally and the absorbed metabolites in rat and human sera. METHODS: After 24 h starvation, 12 rats were divided randomly into two groups, the rats of treated group were given ig Rg1 500 mg.kg^-1 once daily and ip 5% glucose-saline for 3 succesive days. The samples of urine and feces were collected and extracted with ether and methanol, respectively. The extracts were subjected to analyses by TLC, electrospray ionization mass spectrometry (ESI-MS) and HPLC. Another 20 fasted rats were divided randomly into 5 groups. The treated group was given ig Rg1 500 mg.kg^-1 and the control group was given water ig 10 mL.kg^-1. The rats of the control and one treated group were decapitated at 15 min and the rats of the remaining 3 treated groups were killed at 30, 90 and 120 min respectively after drug administration to obtain sera which were extracted with ether for analyses by TLC, HPLC and ESI-MS. RESULTS: Rh₁ and F1 were detected in the urine and sera of rats by ESI-MS and HPLC, while only Rh1 was found in human urine. CONCLUSION: Rg₁ is metabolized in rat and human intestine and its metabolites were found in rat and human sera.