Aim. The Cl-/H+ antiporter ClC-5 has been linked to Dent's disease, an X-linked renal disease associated with low molecular weight proteinuria, hypercalciuria and nephrolithiasis. ClC-5 is expressed on early endosomes of proximal tubule cells, where it is thought to play a critical role in endosomal function. There is a large number of remaining ClC-5 pathogenic mutations that have not been fully investigated. We therefore thought to analyze the functional consequences of four published mutations. Methods. ClC-5 mutants were synthesized from human wild-type (WT) ClC-5 extracellularly HA tagged subcloned into pTLN expression vector (kindly provided by T. J. Jentsch, MDC/FMP, Berlin, Germany) for expression in X. laevis oocytes or into the peGFP expression vector for expression in HEK293 cells. We evaluated electrical activity, sub-cellular targeting and protein expression of WT and mutant ClC-5 by two-electrode voltage-clamp, immunocytochemistry, chemiluminescence and western blot analysis. Results. The L278F mutant showed a reduction of currents by 63% by comparison to those of WT ClC-5 (p<0.001, n=6). Currents recorded with the L225P (n=11), Y272C (n=8) and G513R (n=7) mutants were not significantly different from non-injected (NI) oocytes. These mutants were retained in the endoplasmic reticulum, and displayed reduced protein expression levels in HEK293 transfected cells. By contrast, we found no significant difference between the Y272C and L278F mutants and WT ClC-5 in terms of subcellular targeting and protein expression levels in X. laevis oocytes and HEK293 cells. Conclusion. Two types of ClC-5 mutants can be distinguished. The L225P and G513R mutants display a defective subcellular targeting in X. laevis oocytes and HEK293 cells. The Y272C and L278F mutants have a reduced electrical activity. Further studies should investigate how the regulation or the conduction pathway are involved in the second case of mutations.