PURPOSE OF REVIEW: Sleep and the chronobiological disease cluster headache are believed to be interconnected. Despite efforts, the precise nature of the relationship remains obscured. A better understanding of this relation may lead to more effective therapeutic regimes for patients suffering from this debilitating disease. This review aims to evaluate the existing literature on the subject of cluster headache and sleep. LATEST FINDINGS: Several previous studies describe an association between episodic cluster headache and distinct macrostructural sleep phases. This association was not confirmed in a recent study of seven episodic cluster headache patients, but it was suggested that further studies into the correlation between cluster headache attacks and the microstructure of sleep are relevant. The connection between cluster headache and the hypocretins is currently under investigation. SUMMARY: There is evidence in favour of an association between episodic cluster headache and REM sleep whereas no such relation to chronic cluster headache has been reported. Particular features in the microstructure of sleep and arousal mechanisms could play a role in the pathogenesis of cluster headache. Reports indicate that cluster headache and obstructive sleep apnoea are associated. Single cases show improvement upon treatment of sleep apnoea, but the causal relationship remains in question.