Background. The earthquake that struck the Los Angeles area at 4:31 a.m. on January 17, 1994, was one of the strongest earthquakes ever recorded in a major city in North America. Once the life-threatening situation was over, the Northridge earthquake, so called because its epicenter was near Northridge, California, just north of Los Angeles, provided investigators an unusual opportunity to examine the relation between emotional stress and sudden cardiac death. Methods. We reviewed the records of the Department of Coroner of Los Angeles County for the week before the earthquake, the day of the earthquake, the six days after the earthquake, and corresponding control periods in 1991, 1992, and 1993. Results. On the day of the earthquake, there was a sharp increase in the number of sudden deaths from cardiac causes that were related to atherosclerotic cardiovascular disease, from a daily average (±SD) of 4.6 ± 2.1 in the preceding week to 24 on the day of the earthquake (z=4.41, P<0.001). Sixteen victims of sudden death either died or had premonitory symptoms, usually chest pain, within the first hour after the initial tremor. Only three sudden deaths occurred during or immediately after unusual physical exertion. During the six days after the earthquake, the number of sudden deaths declined to below the base-line value, to an average of 2.7±1.2 per day. Conclusions. The Northridge earthquake was a significant trigger of sudden death due to cardiac causes, independently of physical exertion. This finding, along with the unusually low incidence of such deaths in the week after the earthquake, suggests that emotional stress may precipitate cardiac events in people who are predisposed to such events.