Utilizing a combination of patchclamp and calcium microspectrofluorimetry we have characterized the effects of angiotensin II (Ang II) on intracellular calcium and on the electrical properties of mouse renal juxtaglomerular cells. We found the existence of voltage activated inward and outward rectifying potassium currents, and the inhibition of the anomalous inward rectifying potassium current by Ang II. Blocking the inward rectifyer was paralleled by membrane depolarization, but we obtained no evidence for calcium entry due to voltage-gated calcium channels in JG cells. Instead, under voltage clamp Ang II induced release of calcium from intracellular stores followed by a phase of transmembrane calcium influx and oscillations of intracellular calcium concentrations. Changes in intracellular calcium concentrations were accompanied by prominent calcium-activated chloride currents.