Previous studies have demonstrated variation in vascular events with respect to season and time of day. Changes in barometric pressure display daily and seasonal variations and could modulate the occurrence of vascular events. The objective of this study was to determine whether a relation exists between changes in barometric pressure and occurrence of stroke or acute myocardial infarction (AMI). A retrospective analysis of hospital admissions for AMI and stroke from 1993 to 1996 in central Texas was related to changes in atmospheric pressure that were obtained from the National Climatic Data Center. Patients who had AMI (n = 1,327) or stroke (n = 839) were identified from a computerized hospital database. Mean atmospheric pressure, greatest change in pressure, and rate of change in pressure per 24-hour period were computed. One-, 2-, and 3-day and seasonal groupings of cardiovascular events were related to corresponding changes in barometric pressure. The fall and winter seasons had the highest variability in atmospheric pressure readings. There was a significant correlation (p = 0.0083) between a decrease in atmospheric pressure and the occurrence of AMI the day after a pressure decrease, especially during the fall and winter seasons. No relation between stroke and atmospheric pressure was demonstrated. In conclusion, we conclude that rapid decreases in barometric pressure are associated with the occurrence of AMI but not of stroke.