The present study was designed to observe the properties of swelling-activated chloride channel (I(subscript CLswell) in mouse cardiac myocytes using patch clamp techniques. In whole-cell recordings, hypotonic solution activated a chloride current that exhibited outward rectification, weak voltage-dependent inactivation, and anion selectivity with permeability sequence of I(superscript -)> Br(superscript -)>Cl(superscript -). The current was sensitive to Cl(superscript -) channel blockers tamoxifen, NPPB and DIDS. In single-channel recordings, cell swelling activated a single channel current which showed outward rectification with open probability of 0.76±0.08 and conductance of 38.1±2.5pS at +100mV under [Cl(superscript -)] symmetrical condition. I-V relation revealed the reversal potential as expected for a Cl(superscript -)-selective channel. These results suggested that in mouse cardiac myocytes, swelling-activated, outward rectifying chloride channel with a single channel conductance of 38.1±2.5pS (at +100mV under [Cl(superscript -)] symmetrical condition) underlies the volume regulatory Cl(superscript -) channel.