The aim of this study was to estimate the prevalence of insufficient physical activity and to find the factors associated to this outcome in Lages, Santa Catarina, Brazil (2007). A cross-sectional population-based study was carried out in a representative sample of individuals between 20 and 59 years of age (n=2,051). Physical activity was estimated using the short version of the International Physical Activity Questionnaire. Insufficient physical activity was defined as less than 150 minutes per week spent in moderate or vigorous physical activity. The prevalence of insufficient physical activity was 29.6% (95%CI: 27.6; 31.7). The associated factors were to be male, obese, have high income, and negative self-perception of health status. The prevalence of insufficient physical activity was lower than reported by other Brazilian studies. Studies that distinguish different types of physical activity can contribute to a better understanding of the problem. The implementation of public policies that encourage the practice of regular exercises is required.