The causes of ischaemic stroke in young adults are many and diverse. Such patients usually require more extensive investigations in order to find an underlying cause than more elderly patients. It is important that a comprehensive search is made since many of the underlying disorders are treatable. Principal causes are extracranial arterial dissection, cardioembolism, premature atherosclerosis, haematological and immunological disorders and migraine. Drug abuse is becoming increasingly important but the risk of stroke in pregnancy remains unclear. Isolated angiitis of the central nervous system, heritable disorders of connective tissue and other genetically determined disorders (mitochondrial cytopathies, CA-DASIL) account for a small proportion of ischaemic strokes in the young. Management is probably best undertaken by a physician with a specialist interest and, if full investigation fails to elucidate a definite cause, the risk of future stoke is low.