Despite the vague and permissive nature of the 1969 definition, it was soon recognized that it yielded consistent epidemiological profiles. Large series from several countries and geographic regions reported a similar age distribution curve, sparing the perinatal period, peaking between 2 and 4 months, and declining rapidly thereafter.8,11 Virtually all victims were found dead after being put down to sleep. Other common features included a seasonal distribution, tending to spare the summer months in most years, an association with minor viral inflammation, prematurity, or social disadvantage. A similar degree of uniformity was apparent in the autopsy findings, with most babies having prominent intrathoracic petechiae, pulmonary congestion and edema, minor inflammatory infiltrates usually found in the respiratory tract, fluid blood, and empty urinary bladders. Thus the concept of a true syndrome seemed to be justified when applied to collective series of cases. However, disagreement persisted concerning individual cases.