The aim of this study was to investigate the effects of acarbose and Rumex patientia on liver ultrastructure in streptozotocin (STZ)-induced diabetic (type II) rats. Forty-two-day-old, neonatal Wistar albino rats were used. They were divided into six groups. STZ was injected into groups 4, 5 and 6 on postnatal day 2. Groups I and 5 received water, groups 2 and 6 received 2% decoction of R. patientia grain and groups 3 and 4 received 40 mg acarbose/100 g teed. During the experimental period, blood glucose levels were checked periodically and HbA 1 c levels were measured from cardiac blood at the end of the experiment. In addition, liver tissue was examined by electron microscopy Our results showed that glucose and HbA1c levels, which are Increased by STZ, were decreased by acarbose and R. patientia. In group 5, most of the mitochondria of hepatocytes were swollen and some hepatocytes contained lipid granules in their cytoplasm. In group 4, no pathological changes were observed in hepatocytes, but some lysosomes were found in their cytoplasms. In group 6, mitochondrial changes were minimal compared with those in group 5, and no lipid granules were observed in hepatocytes.