One of the most common concomitants of sleep apnea, daytime sleepiness, may affect driving ability. We used an anonymous self-report questionnaire to examine driving behaviour in three age-matched groups of male subjects. "Controls" (N = 266) were recruited from visitors to the Traffic Authority's stand at Sydney's Royal Easter Show. "Snorers" (N = 341 and "Apneics" (N = 101) were recruited from patients assessed for apnea by overnight sleep study at Royal Prince Alfred Hospital, Hornsby Sleep Disorders Centre and Camperdown Sleep Disorders Centre. Snorers were those who did not have apnea, or had fewer than 10 apneas per hour of sleep. Patients with apnea indices >10 were classified ilsleep apneicl.