The assessment of leisure-time physical activity in four studies that used a similar questionnaire was carried out by the University of Minnesota between 1957-1960 and 1985-1987. Each study included adults living in the Upper Midwest. In men, age-adjusted leisure-time energy expenditure consistently increased over time, with the greatest increase occurring between 1957-1960 and 1974-1975. Much of this increase occurred in moderate and heavy intensity activity and was greater for white collar workers than for blue collar workers. The increase in the last period was similar for both classes of workers. Data were unavailable for women before 1980. Age-adjusted leisure-time physical activity in women also increased between 1980-1982 and 1985-1987. This increase was greater for blue collar than for white collar women. A major strength of these analyses is the last two surveys, which were specifically designed to assess time trends. Exact comparability of the earlier two surveys with the two latter surveys cannot be established; however, the use of the same detailed questionnaire across 30 years is unique. We conclude that leisure-time physical activity has been increasing for three decades, including substantial increases in vigorous activities.