The short-term relationship between winter temperatures and cardiac disease mortality in Cape Town was investigated for the period 1978-1985. The mortality data were stratified according to age (0-4 years, 5-59 years, 60 years and older), while the temperature data comprised daily maximum and minimum temperatures at Cape Town International Airport. The analyses identified a strong lagged relationship between extreme (high and low) temperatures and daily mortality, and it was established that large daily temperature variations were associated with above-average mortality rates.