The prevalence of sleep-related disorders (SRD) in adults in Turkey is unknown. The main objective of our study was to assess the prevalence of SRD in Sivas, Turkey. Adults living in Sivas, a city of Turkey from the central region of Anatolia at 20-107 years of age, in both genders, of the 5339 persons, who attended the survey 2638 (49.4%) were male and 2701 (50.6%) were female. The prevalence of insomnia, habitual snoring, obstructive sleep apnea (OSA) and day time hyper somnolence was 40.3%, 37.0%, 6.4%, 24.0% respectively. The prevalence rates of narcolepsy and nocturnal myoclonus was 30.6%, 40.1% respectively. There was a statistical significance between the persons of above 60 years old and another age groups (p< 0.05). But we did not find any significant difference between smokers and non-smokers, also between males and females about SRD prevalence (p> 0.05). However, sleep apnea prevalence was about 9 times higher in the persons suffering from hypertension than without hypertension. Also sleep apnea prevalence was 12 times higher in the persons suffering from overweight. This study has shown that sleep-disordered breathing (SDB) prevalence in Turkey is as high as in other countries and may be more common.