To evaluate the presence of sleep symptoms in Machado-Joseph disease/spinocerebellar ataxia type 3 (MJD/SCA3). We used a sleep questionnaire and the Epworth Sleepiness Scale to compare 53 patients with MJD/SCA3 and 106 controls. Patients with MJD/SCA3 reported more symptoms of insomnia, restless leg syndrome and REM sleep behavior disorder as well as nocturnal cramps, snoring and nocturnal apnea. Insomnia was the most frequently reported sleep-related complaint in the MJD/SCA3 group. Our results indicate that sleep disorders are common in patients with MJD/SCA3 and probably have a multifactorial etiology, with components of a primary sleep disorder in addition to sleep-disrupting symptoms such as nocturia and cramps.