Here, we characterized six Best vitelliform macular dystrophy (BVMD)-associated BEST1 dominant mutations by documenting the patients’ phenotypes, examining the subcellular localization of endogenous BEST1 and surface Ca2+-dependent Cl− currents in patient-derived RPEs, and analyzing the functional influences of these mutations on BEST1 in HEK293 cells. This evidence concerns the gene BEST1 and Best vitelliform macular dystrophy.