In non-excitable cells, stimulation of phosphoinositide (PI) turnover and inhibition of the endoplasmic reticulum (ER) Ca 2ฯฉ -ATPase are methods commonly used to deplete calcium stores, resulting in a capacitative Ca 2ฯฉ influx (i.e., Ca 2ฯฉ releaseactivated Ca 2ฯฉ influx). Since this Ca 2ฯฉ influx in glial cells has not been thoroughly investigated, we have used C 6 glioma cells as a glial cell model to study this phenomenon. On adding cyclopiazonic acid (CPA) or thapsigargin (TG) (two ER Ca 2ฯฉ -ATPase inhibitors) in Ca 2ฯฉ -free medium, only a small transient increase in intracellular Ca 2ฯฉ was seen. After depletion of the stored Ca 2ฯฉ , a marked Ca 2ฯฉ influx, followed by a prolonged plateau, was seen on re-addition of extracellular Ca 2ฯฉ ions (2 mM), i.e., capacitative Ca 2ฯฉ influx. A similar effect was seen on adding ATP, known to deplete the inositol triphosphate (IP 3 )-sensitive Ca 2ฯฉ store in C 6 cells. After various degrees of store depletion, the amplitude of the capacitative Ca 2ฯฉ influx was found to be highly dependent on the amount of Ca 2ฯฉ remaining in the store. This Ca 2ฯฉ influx was markedly inhibited by (1) La 3ฯฉ and Ni 2ฯฉ , (2) SK&F 96365, econazole, and miconazole, and (3) membrane depolarization, clearly showing that this Ca 2ฯฉ influx after store depletion in C 6 cells is a capacitative mechanism. Interestingly, the capacitative Ca 2ฯฉ influx can be inhibited by a reduction in intracellular ATP (ATP i ) levels in glial cells. The role of ATP i in the capacitative Ca 2ฯฉ influx is discussed.