BACKGROUND: Short-term changes in temperature have been associated with cardiovascular deaths. This study examines changes in this association over time among the US elderly. METHODS: Daily cardiovascular mortality counts from 107 cities in the US National Morbidity and Mortality Air Pollution Study were regressed against daily temperature using the case-crossover method. Estimates were averaged by time and season using a meta-analysis. RESULTS: In summer 1987 the average increase in cardiovascular deaths due to a 10¡F increase in temperature was 4.7%. By summer 2000, the risk with higher temperature had disappeared (-0.4%). In contrast, an increase in temperature in fall, winter and spring was associated with a decrease in deaths, and this decrease remained constant over time. CONCLUSIONS: Heat-related cardiovascular deaths in the elderly have declined over time, probably due to increased use of air conditioning, while increased risks with cold-related temperature persist.