The acute negative inotropic and chronotrophic effects of aqueous and alcoholic garlic extracts (Allium sativum L.) on spontaneous and adrenalin-stimulated contractions of the Wistar rat atria were investigated. The addition of garlic extracts to isolated rat atria evoked negative inotropic and chronotropic effects. Ethanolic garlic extract exerts much stronger negative inotropic (58.33 +/- 14.76%) effects than aqueous extract (43.66 +/- 16.32%). The difference in frequency reduction is especially conspicuous. Aqueous garlic extract very slightly affects the frequency, while ethanolic extract reduces it by more than 40%. In addition to these effects, the positive inotropism and chronotropism induced by the addition of noradrenaline, were much more antagonized by ethanolic garlic extract than by aqueous extract. Moreover, ethanolic garlic extract establishes sinus rhythm in the atria with extrasystoles induced by noradrenaline.