The prevalence of sleep complaints in adults in a primary care setting is > 10%. The most frequently seen condition by far is that of primary insomnia, which affects 10% of adults on a chronic basis. In contrast to primary insomnia, in which most patients report tiredness and fatigue during the day but are unable to sleep during the day either, the second most frequent sleep disorder encountered, obstructive sleep apnoea, is typified by excessive daytime sleepiness. Patients with primary insomnia or fatigue syndromes typically will score low on the Epworth Sleepiness Scale (ESS < 3) whereas those with organic sleep pathologies or sleep restriction will score higher. A score > 10 is seen as 'pathological', with a mean ESS in the population of 5-6.