The plant Mentha spicata, or peppermint, is commonly used in the treatment of loss of appetite, common cold, bronchitis, sinusitis, fever, nausea and vomiting, and indigestion as a herbal agent. In this study, we aimed to investigate the biochemical and histological effects of M. spicata Labiatae, growing on the Ananias high plateau of Yenisarbademli town, on rat uterine tissue. Twenty female Wistar albino rats weighing 160 +/- 10 g were used for this study. Rats were divided into two groups of ten animals: group I received no herbal tea (control group) and group II received 20 g/L M. spicata tea. Control group rats were given commercial drinking water (Hayat DANONESA water). Herbal tea was prepared daily and provided at all times to the rats over 30 days as drinking water. Plasma malondialdehyde (MDA) levels were determined. In addition, uterine tissues were submitted for histopathologic examination. MDA levels were increased in group 11 when compared with the control group. The difference between group 11 and the control group was statistically significant (P < 0.01). In the M. spicata Labiatae-treated group, histopathological changes like apoptosis and diffuse eosinophil leucocyte infiltration in surface and stromal glandular epithelium were observed in both endometrium and endocervix. It was concluded that lipid peroxidation and uterine damage occurs after M. spicata administration in rat uterus. Despite the beneficial effects of M. spicata Labiatae in indigestion, we should also be aware of the toxic effects when it is not used in the recommended fashion, at the recommended dose.