The effects of voltage-dependent Ca2+ current (ICa) on resting and gamma-aminobutyric acid (GABA)-gated Cl- conductances were studied in isolated frog sensory neurons. The amplitude of GABA-gated Cl- current (ICl) was greatly suppressed by a preceding ICa. The GABA dose-response curve was shifted to the right without changing the maximum response by increasing [Ca2+]i. An ICa-activated ICl was observed as an inward tail current on the 'off' phase of ICa. This tail current was easily saturated by increasing the amount of Ca2+ influx.