We described a patient with clinical findings from Kennedy's disease and positive genetic study for Kugelberg-Welander's disease. A 24 years old man with negative family history presented with progressive spinal and bulbar muscular atrophy and gynecomastia at the age of 14. He was clinically diagnosed as having Kennedy's disease. However, a genetic study performed later was found to be negative for this disease and was positive for Kugelberg-Welander's disease, with deletion of the exons 7 and 8 in the "survival of motor neuron" gene.