Insomnia and stress are two conditions, which are strongly associated and appear to be pathophysiologically integrated: the occurrence of stress increases the risk of insomnia, insomnia exacerbates stress, and coexistence of both factors has a negative influence on their prognosis. Stress and insomnia thus share complex interactions and the mechanisms involved are insufficiently understood but involve both psychological and physiological processes. First choice interventions involve behavioural and cognitive strategies and, to a lesser extent, pharmacological treatment.