In industrial countries, sudden infant death syndrome (SIDS) poses the most common mode of deaths occurring in the postneonatal period. During the last years the incidence has decreased and is currently less than 0.5 per 1000 live births. The cause of SIDS is still unknown. One theory claims that SIDS is due to suffocation caused by failure of central respiratory control, CO(2) rebreathing or airways obstruction. Further pathological factors including hyperthermia as well as impairment of the sleeping- and waking centre are in discussion. The most important risk factors include lying prone, heat exposure of the child, premature delivery, maternal age less than 18 years, smoking and drug abuse during pregnancy and the absence of breast feeding. SIDS is not an entity but a descriptive term for sudden and unexpected deaths in infancy without adequate cause of death being established by methods currently used. SIDS in forensic medicine is not only important because of its relative frequency, but also because of the differential diagnoses which have to be considered in each case. Therefore other natural and unnatural causes of death have to be explored by autopsy and careful postmortal examination (histological, toxicological, microbiological and virological analysis), taking into account circumstances at the death scene and medical history of the infant.