We report a family with Machado-Joseph disease (MJD) that was previously diagnosed with dentatorubral-pallidoluysian atrophy (DRPLA), on the basis of the neuropathologic findings. Because the clinical and pathologic reevaluation strongly suggested a diagnosis of MJD, we conducted a genetic study in the family. Two patients, aged 38 and 40, revealed CAG repeat lengths of the MJD1 gene of 80, 28 and 75, 14, confirming a final diagnosis of MJD.