We recorded Ca 2+ current and intracellular Ca 2+ ([Ca 2+ ] i ) in isolated adult rat dorsal root ganglion (DRG) neurons at 20 and 30°C. In neurons bathed in tetraethylammonium and dialyzed with cesium, warming reduced resting [Ca 2+ ] i from 87 to 49nM and the time constant of the decay of [Ca 2+ ] i transients (τ r ) from 1.3 to 0.99s (Q 10 =1.4). The Buffer Index, the ratio between Ca 2+ influx and Δ[Ca 2+ ] i ∫ICa dt/Δ[Ca2+]i, increased two- to threefold with warming. Neither inhibition of the plasma membrane Ca 2+ -ATPase by intracellular sodium orthovanadate nor inhibition of Ca 2+ uptake by the endoplasmic reticulum by thapsigargin plus ryanodine were necessary for the effects of warming on these parameters. In contrast, inhibition of the mitochondrial Ca 2+ uniporter by intracellular ruthenium red largely reversed the effects of warming. Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP, 500nM) increased resting [Ca 2+ ] i at 30°C. Ten millimolar intracellular sodium prolonged the recovery of [Ca 2+ ] i transients to 10–40s. This effect was reversed by an inhibitor of mitochondrial Na + /Ca 2+ -exchange (CGP 37157, 10μM). Thus, mitochondrial Ca 2+ uptake is necessary for the temperature-dependent increase in Ca 2+ buffering and mitochondrial Ca 2+ fluxes contribute to the control of [Ca 2+ ] i between 50 and 150nM at 30°C.