Sudden infant death syndrome (SIDS) is defined as the sudden unexpected death of an infant < 1 year of age, with onset of the fatal episode apparently occurring during sleep, that remains unexplained after a thorough investigation, including performance of a complete autopsy and review of the circumstances of death and the clinical history. Despite declines in incidence during the past two decades following the Back to Sleep campaigns, SIDS remains the leading cause of death for infants in developed countries. Epidemiological studies have identified modifiable risk factors such as prone and side sleep positions, smoke exposure, bed sharing, soft bedding and overheating. Pacifier use at sleep time is associated with decreased risk of SIDS. The cause of sudden infant death syndrome is unknown, but it is generally accepted that SIDS likely marks the end of a series of risk factors and pathophysiological responses. Given the complexity of the SIDS research, the following literature review represents only a brief overview of the epidemiology, pathology and pathogenesis of SIDS, focusing on brainstem abnormality, long QT-interval, infection and hypoxemia. Controversial issues regarding the classification and diagnosis are discussed.