Spinal and bulbar muscular atrophy (SBMA) is an X-linked, lateonset neuroendocrine disorder resulting from an expansion of a CAG repeat in the androgen receptor gene. Reported here is a detailed phenotypic study in a series of seven patients from the same family with SBMA with 50 to 54 CAG repeats, juvenile onset ( mean age at onset 13 years [ 8 to 15 years]), and rapid progression leading to compromised ambulation in the mid-20s.