This study investigated the effects of oral administration of extract of green tea (Camellia sinensis) and ginseng (American ginseng-Panax quinquefolium L.), given alone or together, on pancreatic beta-cells, blood glucose, insulin, cholesterol and triglyceride levels in rats with experimental diabetes induced by a single injection of Streptozotocin (STZ) (60 mg kg(-1), i.p.). Fifty adult Wistar Albino rats were used, 10 in each of these five treatment groups: Group A: healthy controls, Group B: STZ-induced diabetes (untreated), Group C: STZ-induced diabetes plus green tea extract (100 mg/kg/daily), Group D: STZ-induced diabetes plus ginseng root (400 mg/kg/daily) and Group E: STZ-induced diabetes plus ginseng root + green tea extracts as before. At the end of the 6 weeks experiment, blood samples were analysed for blood glucose, insulin, cholesterol and triglyceride levels and samples of pancreatic tissue were examined histochemically and immunohistochemically for endocrine islets and beta-cells. Overall, body weight decreased in groups B and C, serum insulin concentrations decreased slightly in groups C-E and total triglyceride levels of blood decreased significantly (p<0.05) in groups B and C compared with control, D and E groups. Histopathological examination showed that degenerative changes in pancreatic beta-cells in STZ-treated rats were minimised to near normal morphology by administration of ginseng (Group D) and ginseng+green tea (Group E) and there was increased intensity of immunohistochemical staining for insulin in these groups. Degeneration of islets of Langerhans beta-cells and weak insulin staining was observed for green tea alone (Group C). These findings demonstrate that ginseng or combined ginseng + green tea decreases blood glucose levels in diabetic rats and increases preservation of P-cells, perhaps by lowering oxidative stress.