This paper develops a profile of the inactive population in Ontario. The findings were based on an analysis of data from the 1990 Ontario Health Survey. A Physical Activity Index, including frequency, duration, and an estimate of intensity, was used to classify individuals on the basis of their leisure time physical activity levels. Inactive comprised the group estimated to average less than 1.5 kcals/kg/day of energy expenditure. Multiple logistic regression was used to estimate the odds of inactivity for a number of predictor variables. Age, gender, friends' participation, perceived health status, and perceived future health problems were the strongest predictors of physical inactivity. The findings contribute to a further understanding of the factors influencing physical activity participation and promotion.