Circadian rhythm sleep disorders are common in clinical practice, and occur when individuals attempt to sleep at the wrong circadian time. They are typically due to alteration in the functioning of the internal circadian timing system (eg delayed or advanced phase sleep disorder), or changes in the external environment (eg shift work sleep disorder, jet-lag). Patients su ering from circadian rhythm sleep disorders complain of insomnia and excessive daytime sleepiness that lead to impairment in their functioning and reduced quality of life. The main aim of the therapy should be restoration of disturbed circadian sleep-wake rhythm and/or reinforcement of circadian signals. Bright light exposure and exogenous melatonin administration, applied at a correct circadian time, are considered to be the treatment of choice for these sleep disorders. Recent studies indicate that newly developed drugs with high a nity for melatonin receptors may be well useful in the treatment of circadian rhythm sleep disorders.Keywords: sleep disorders, insomnia, circadian rhythms, melatonin, light therapy.