Intracellular Ca(2+) distribution and its dynamics are essential for various cellular functions. We show with single HeLa cells that a microscopic heat pulse induces Ca(2+) uptake into intracellular stores during heating and Ca(2+) release from them at the onset of recooling, and the overshoot of Ca(2+) release occurs above the critical value of a temperature change, which decreases from 1.5 to 0.2 degrees C on increasing the experimental temperature from 22 to 37 degrees C. This highly thermosensitive Ca(2+) dynamics is probably attributable to the altered balance between Ca(2+) uptake by endoplasmic reticulum Ca(2+)-ATPases and Ca(2+) release via inositol 1,4,5-trisphosphate receptors. These results suggest that Ca(2+) signaling is extremely sensitive to temperature changes, especially around body temperature, in cells expressing inositol 1,4,5-trisphosphate receptors.