The safety of bayacon, a new drug based on Baikal aconite intended for the treatment of inflammation-proliferative dermatitis (psoriasis), was studied on a preclinical level. With respect to a single introduction in rats and mice, the drug is classified as a low-toxicity substance. However, a 3-month oral administration of bayacon (0.25, 0.5, and 2.5 mg/kg) in rats showed a number of dose-dependent functional and morphological changes. A dose of 2.5 mg/kg induced weak hyporegenerative anemia, neutrophile leukocytosis, and dystrophic changes in the stomach mucosa, heart, liver, and kidneys. All these symptoms disappeared within two weeks after abolition of the drug. Oral administration of bayacon (0.1 and 0.5 mg/kg) in rabbits produced no pathological morphofunctional changes in the organs and tissues studied. In rats, bayacon 2.5, 0.5, and 0.25 mg/kg doses of bayacon led to dose-dependent changes in some characteristics of the reproduction system. The drug did not influence the expression of allergic reactions and showed no immunotoxicity and mutagenicity manifestations.