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Astrocytes, a subtype of glial cells, have numerous characteristics that were previously considered exclusive for neurons. One of these characteristics is a cytosolic [Ca²⁺] oscillation that controls the release of the chemical transmitter glutamate and atrial natriuretic peptide. These chemical messengers appear to be released from astrocytes via Ca²⁺‐dependent exocytosis. In the present study, patch‐clamp membrane capacitance measurements were used to monitor changes in the membrane area of a single astrocyte, while the photolysis of caged calcium compounds by a UV flash was used to elicit steps in [Ca²⁺]_i to determine the exocytotic properties of astrocytes. Experiments show that astrocytes exhibit Ca²⁺‐dependent increases in membrane capacitance, with an apparent K_d value of ∼20 μM [Ca²⁺]_i. The delay between the flash delivery and the peak rate in membrane capacitance increase is in the range …