Background:In recent years, it has been noted that children and youth are physically inactive, and physical activity levels have declined over the past decades. However, few empirical studies have been conducted to test this assumption. Therefore, the purpose of this study was to examine leisure-time physical activity levels among Canadian adolescents 12–19 years of age.Methods:Age, sex, geographic, and temporal trends in leisure-time physical activity energy expenditure (AEE) were examined using data from 5 national surveys conducted between 1981 and 1998. AEE was calculated from participants’ questionnaire responses on physical activity participation. General linear models were used to examine the differences in AEE across survey years, geographic regions, sexes, and age groups.Results:Males and 12–14-year-olds displayed greater AEE than females and 15–19-year-olds, respectively, and AEE was lowest in Quebec and highest in the West. AEE increased between the 1981 and 1988 surveys and has since remained relatively stable. The prevalence of subjects meeting the 12.6 kJ · kg−1 · d−1 (3 kcal · kg−1 · d−1) recommendation increased from 1981 to 1988. Since 1988, the prevalence of those meeting the 12.6 kJ · kg−1 · d−1 recommendation has decreased in 12–14 year old boys and remained relatively stable in the other groups. In 1998, about 45% of males and 35% of females met the 12.6 kJ · kg−1 · d−1 recommendation. In 1998, about 20% of 12–19-year-old males and 12–14-year-old females met the 25.1 kJ · kg−1 · d−1 (6 kcal · kg−1 · d−1) recommendation, while about 10% of 15–19-year-old females met this recommendation. In females, the prevalence of those meeting the 25.1 kJ · kg−1 · d−1 recommendation has remained relatively stable (about 10%) since 1981 except for an increase between 1996 and 1998 in 12–14-year-old girls. In males, a similar pattern, but not as dramatic, of that observed for the prevalence of those meeting the 12.6 kJ · kg−1 · d−1 emerged—that is, an increase between 1981 and 1988 and then a decrease in 12–14-year-old boys and a stable pattern in 15–19-year-old boys.Conclusion:Although self-reported leisure-time physical activity appears to have increased since 1981, a majority of Canadian adolescents do not meet current recommendations for physical activity.