The effects of Cd²⁺ on spontaneous contraction, and the contractures induced by 0mM Na⁺, 60mM K⁺ and 10^-6 M acetylcholine, 1mM caffeine were studied in order to elucidate diverse actions of Cd²⁺ on the Ca²⁺ mobilization related with contractility in the antral circular muscle of guinea pig stomach. Cd²⁺ inhibited the spontaneous contraction in a does dependent manner (10^-6 M 10^-4 M). Cd²⁺ (3 X 10^-5M) suppressed 60 mM K⁺ induced contracture composed or a phasic and a tonic response and the increased tonic response by the increased external Ca²⁺ concentration. Cd²⁺ also suppressed acetylcholine induced contracture composed of repetitive phasic and a tonic component and the increased tonic response by the increased external Ca²⁺ concentration. Caffeine in the concentration of 1mM evoked contracture but Cd²⁺ suppressed the contracture. Cd²⁺ suppressed the amplitude of the Na⁺ tee contracture dose dependently and the amplitude of Na⁺ free contracture almost decreased to 20% of control amplitude in the concentration of 10^-4 M Cd²⁺. From the above results, it is suggested that Cd²⁺ may inhibit not only Ca²⁺ influx via voltage sensitive, receptor operated Ca²⁺ channel and Na/ca exchange but also intracellular Ca²⁺ release from the sarcoplasmic reticulum in the antral circular muscle of guinea pig stomach.