INTRODUCTION: Insomnia is common among the elderly. The use of hypnotic drugs in elderly patients is frequently criticized owing to dependency, cognitive impairments, falls and withdrawal effects. The production of melatonin, a physiological sleep and circadian rhythm regulator, declines with age. Prolonged-release melatonin (Circadin®), designed to mimic the endogenous pattern of melatonin production, is licensed for insomnia in patients aged ≥ 55 years. AREAS COVERED: This review summarizes published studies on Circadin's efficacy and safety (Summary of Product Characteristics and Medline search on 'Circadin' and 'insomnia'). EXPERT OPINION: The main significant and clinically relevant benefits are improvements in sleep quality and latency, next-day morning alertness and quality of life. The responses may develop over several days. An oral 2-mg dose once daily, for 3 months, has generally been well tolerated with no rebound, withdrawal or 'hangover' effects and no safety concerns on concomitant therapy with antihypertensive, antidiabetic, lipid-lowering or anti-inflammatory drugs. Untoward effects of hypnotics on cognition, memory, postural stability and sleep structure are not seen with Circadin. Given as a first-line prescription, with 13 weeks' posology and the lack of rebound effects, Circadin has the potential to improve quality of life in insomnia patients aged 55 years and older and avoid long-term use of hypnotics.