The present experiment was conducted to see whether or not several cardioactive agents influence the regenerative Ca⁺⁺ release in the mechanically disrupted cardiac cells. The mechanically disrupted cardiac cells were prepared by the method of Kerrick and Best from the ventricle of rat. The tension development of the disrupted cardiac cells was measured with a mechanoelectric transducer (RCA 5734). The results were summarized as follows 1) 2 mM caffeine enhanced the regenerative Ca⁺⁺ release, whereas 2 mM Procaine inhibited the Ca⁺⁺ release as reported by other investigators. 2) Epinephrine at concentrations of 10^-7, 10^-6 and 10^-5M increased the regenerative Ca⁺⁺ release significantly but showed a poor dose response on the Ca⁺⁺ release. 3) Propranolol showed no effect on the regenerative Ca⁺⁺ release when studied alone. Furthermore, it showed no antagonistic effect on an increased regenerative Ca⁺⁺ release induced by epinephrine. 4) Other cardioactive agents such as acetylcholine, ouabain, isoproterenol and c-AMP at concentrations of 10^-6M showed no effect on the regenerative Ca⁺⁺ release. From the above results, it may be concluded that the cardioactive actions of these agents are not related directly to the process of regenerative Ca⁺⁺ release.