Calcium binding and release by sarcoplasmic reticulum vesicles of guinea pig heart were studied by means of a dialysis apparatus and analyzed with a model of three closed compartments. The rate constants of calcium binding were increased by taurine, and this effect was dose-related, whereas calcium efflux rate constants were very near to 0 in control experiments and were not effected by taurine. Taurine therefore increased the calcium content of sarcoplasmic vesicles and decreased the calcium concentration of the medium. beta-Alanine had no action on calcium fluxes.