This study investigated expression of the volume-activated chloride current and its relationship with RVD capacity in the cell cycle in nasopharyngeal carcinoma cells (CNE-2Z) using patch-clamping and cell image analysis techniques. Hypotonic challenge caused CNE-2Z cells to swell and activated a chloride current with a linear conductance, negligible time-dependent inactivation and a reversal potential close to the Cl^-equilibrium potential. The sequence of anion permeability was was I^- > Br^- > Cl^- > gluconate. Chloride channel blockers, tamoxifen, NPPB and ATP, inhibited the volumeactivated chloride currents. Flow cytometric analysis showed that highly synchronous cells were obtained by the mitotic shake-off technique and by a double chemical-block (thymidine and hydroxyurea) technique: 85% of cells were in G0/G1 4 h after reincubation of shake-off cells, and 86% of the population had progressed into S-phase 4h after release from the double chemical-block. M-phase cells were distinguishable from the cell population by their condensed chromosomes visible under the phase-contrast microscope. The expression of volume-activated chloride currents was cell cycle dependent. The activity of volume-activated chloride channels were high in G1-phase, down-regulated in S-phase, but increased in M-phase. The current amplitude in G1-phase was more than twice that in S-phase. Hypotonic solution also activated RVD which was cell cycle dependent and was inhibited by the chloride channel blockers NPPB, tamoxifen and ATP. The expression of the volume-activated chloride currents was closely correlated with the RVD capacity in the cell cycle suggesting a functional relationship. Inhibition of the volume-activated chloride current by NPPB (100µM) arrested cells in G0/G1. The data also suggest that expression of the volume-activated chloride currents and RVD capacity are actively modulated during the cell cycle. The volume-activated Cl^- current associated with RVD may therefore play an important role during the cell cycle progress in CNE-2Z cells.