Spontaneous release of Ca²⁺ from the sarcoplasmic reticulum (SR) of cardiac cells and the subsequent intracellular Ca²⁺ 2+ fluxes associated with Ca²⁺ waves measured in rabbit ventricular myocytes both in terms of cytoplasmic and intra-SR Ca²⁺ on the basis of fluorescence measurements using confocal fluorescence microscopy. The role of with Ca²⁺ waves in terms of promoting cellular with Ca²⁺ efflux will be also be discussed including the modulation of this efflux by calcium/calmodulin dependent protein (CaM) kinase. The relationship between Ca²⁺ waves and the underlying Ca²⁺ spark event will also be described along with the recent evidence that non-spark Ca²⁺ release is an important for Ca²⁺ wave initiation and propagation. Ca²⁺ sparks arise from regular arrays of clusters of ryanodine receptors while the non-spark SR Ca release may arise from "rogue" ryanodine receptors that represent a novel target for antiarrhythmic therapy.