Jogging is one of the most popular forms of vigorous exercise, but its effect on longevity has not been documented. This analysis comprise a random sample of 4658 men aged 20-79 years with no prior myocardial infarction, who participated in the first (1976-1978) and second (1981-1983) examination of the Copenhagen City Heart Study. They were entered in the mortality analysis at the second examination and were followed up until 30 November 1998. The influence of jogging on time to death was analysed by Cox regression, with age as the time axis. In addition to jogging, the model included diabetes, smoking, household income, education, and alcohol consumption as potential confounding variables, and systolic blood pressure, total cholesterol, HDL cholesterol, and BMI as intermediate variables. At the first examination, 217 men (4.7%) reported active jogging. Of these, 96 (2.1%) were still joggers five years later. Overall, 4335 men were non-joggers at both examinations. A significant effect of jogging was found only for the group that were joggers at both examinations, relative risk 0.37 (95% confidence interval, 0.19 to 0.71; p = 0.003). We have found that regular joggers have a significantly lower mortality than have non-joggers. This could also be due to other lifestyle factors, but numerous studies have pointed towards a beneficial effect of physical activity on health. The optimal intensity, frequency, and duration of physical activity has yet to be established.