This study determined whether whole cell Ca²⁺ transients and unitary SR Ca²⁺ release events are constant throughout adult life or whether Ca²⁺ release is altered in aging ventricular myocytes. Myocytes were isolated from young adult (~5 months) and aged (~24 months) mice. Spontaneous Ca²⁺ sparks and Ca²⁺ transients initiated by field-stimulation were detected with fluo-4. All experiments were conducted at 37^oC. Ca²⁺ transient amplitudes were reduced and Ca²⁺ transient rise times were abbreviated in aged cells stimulated at 8 Hz compared to young adult myocytes. Furthermore, the incidence and frequency of spontaneous Ca²⁺ sparks was markedly higher in aged myocytes compared to young adult cells. Spark amplitudes and spatial widths were similar in young adult and aged myocytes. However, spark half-rise times and half-decay times were abbreviated in aged cells compared with younger cells. Resting cytosolic Ca²⁺ levels and SR Ca²⁺ stores were assessed by rapid application of caffeine in fura-2 loaded cells. Neither resting Ca²⁺ levels nor SR Ca²⁺ content differed between young adult and aged cells. Thus, increased spark frequency in aging cells was not attributable to increased SR Ca²⁺ stores. Furthermore, the decrease in Ca²⁺ transient amplitude was not due to a decrease in SR Ca²⁺ load. These results demonstrate that alterations in fundamental SR Ca²⁺ release units occur in aging ventricular myocytes and raise the possibility that alterations in Ca²⁺ release may reflect age-related changes in fundamental release events rather than changes in SR Ca²⁺ stores and diastolic Ca²⁺ levels.