CLH-3a and CLH-3b are swelling-activated, alternatively spliced C. elegans ClC anion channels that have identical membrane domains but exhibit marked differences in their cytoplasmic N- and C-termini. The major differences include a 71 amino acid CLH-3a N-terminal extension and a 270 amino acid extension of the CLH-3b C-terminus. Splice variation gives rise to channels with striking differences in voltage, pH and Cl^- sensitivity. Based on structure/function insights gained from crystal structures of bacterial ClCs, we suggested previously that these functional differences are due to alternative splicing of the C-terminus that may change the accessibility and/or function of pore-associated ion-binding sites. We recently identified a mutant worm strain harboring a C-terminal deletion mutation in the clh-3 gene. This mutation removes 101 C-terminal amino acids unique to CLH-3b and an additional 64 upstream amino acids shared by both channels. CLH-3b is expressed in the worm oocyte allowing us to characterize the mutant channel, CLH-3bC, in its native cellular environment. CLH-3bC exhibits altered voltage-dependent gating and pH and Cl^- sensitivity that resemble CLH-3a. This mutation also alters channel inhibition by Zn²⁺, prevents ATP depletion-induced activation and dramatically reduces volume sensitivity. These results suggest that the deleted C-terminal region of CLH-3bC functions to modulate channel sensitivity to voltage and extracellular ions. This region also likely plays a role in channel regulation and cell volume sensitivity. Our findings contribute to a growing body of evidence indicating that cytoplasmic domains play key roles in the gating and regulation of eukaryotic ClCs.