An inwardly rectifying swelling- and meiotic cell cycle-regulated anion current carried by the ClC channel splice variant CLH-3b dominates the whole cell conductance of the C. elegans oocyte. Oocytes also express a novel outwardly rectifying anion current termed I_Cl,OR. We recently identified a worm strain carrying a null allele of the clh-3 gene and utilized oocytes from these animals to characterize ICl,OR biophysical properties. The I_Cl,OR channel is strongly voltage dependent. Outward rectification is due to voltage dependent current activation at depolarized voltages and rapid inactivation at voltages more hyperpolarized than ~+20 mV. Apparent channel open probability is zero at voltages <+20 mV. The channel has a 4:1 selectivity for Cl^- over Na⁺ and an anion selectivity sequence of SCN > I > Br > Cl > F. I_{Cl, OR} is relatively insensitive to most conventional anion channel inhibitors including DIDS, DNDS, 9-AC and NPPB. However, the current is rapidly inhibited by niflumic acid, metal cations including Gd³⁺, Cd²⁺ and Zn²⁺, and bath acidification. The combined biophysical properties of I_{Cl, OR} are distinct from those of other anion currents that have been described. During oocyte meiotic maturation, ICl,OR activity is rapidly downregulated suggesting that the channel may play a role in oocyte Cl^- homeostasis, development, cell cycle control and/or ovulation.