Both endoplasmic reticulum (ER) Ca2+ release and Ca2+ influx are essential components of intracellular Ca2+ ([Ca2+]i) regulation in neuronal cells. Previous studies in non-neuronal cells have shown that an acidotic state inhibits Ca2+ influx via L-type Ca2+ channels, while alkalosis increases influx. Glutamate has also been shown to cause dysregulation of Ca2+ influx. Store operated calcium entry (SOCE) that occurs following depletion of ER Ca2+ stores is a newly defined mechanism in neurons. In this study, we examined the effects of altered pH and of glutamate on SOCE in differentiated rat pheochromocytoma (PC12) cells, a model for neuronal cells loaded with the Ca2+ indicator fura-2. Cells were exposed to zero Ca2+ Tyrode's solution (pH 7.4) with 5 μM cyclopiazonic acid (CPA) to deplete the ER. 20 μM KBR-7943 was used to inhibit Na+/Ca2+ exchange. SOCE was then triggered by reintroduction of 2.5 mM Ca2+ Tyrodes (pH 7.4). The cells were washed and the protocol repeated with altered pH (6.6–7.8; one pH change per protocol), altered temperature (35–39 °C) and with different concentrations of glutamate. SOCE was progressively inhibited with decreased pH or temperature, while alkalosis and increased temperature stimulated influx (p<0.05, ANOVA with repeated measures). Increasing glutamate concentrations progressively inhibited SOCE. These data show that SOCE in PC12 cells is susceptible to acidosis, temperature, and agonist stimulation: factors that can adversely affect neuronal function under pathological conditions. Accordingly, altered SOCE function may contribute to neuronal Ca2+ overload under such conditions. Supported by the Departments of Anesthesiology, and Physiology and Biomedical Engineering, Mayo Clinic.