The immunofluorescence approach, the confocal microscopy and the patch-clamp technique were used to investigate the expression of ClC-3 (one of the candidates of volume-activated chloride channels) and its relationships with the volume-activated chloride current and the capacity of regulatory volume decrease (RVD) in the cell cycle of nasopharyngeal carcinoma cells (CNE-2Z cells). The results indicated that CNE-2Z cells expressed ClC-3. ClC-3 was located predominantly inside the cells but not in the membrane. Both the expression level and the distribution of ClC-3 were cell cycle dependent. ClC-3 expression was low in G1 but high in S phase. The cells in G2/M phase possessed an intermediate level of the expression. ClC-3 expression level was negatively correlated to the RVD capacity and amplitude of the volume-activated chloride current in the cell cycle. The results suggest that ClC-3 may be an important factor in the regulation of cell cycle progression, but that it is probably not the chloride channel associated with RVD in these cancer cells.