The study evaluated the associations of body fatness, TV-watching time, and physical activity with the occurrences of asthma and respiratory symptoms in schoolchildren in Taipei, Taiwan. A questionnaire survey was conducted to elicit episodes of respiratory symptoms and data on lifestyle and anthropometric factors in 2290 5th-grade schoolchildren. Results show that overweight was positively associated with 5 of the 7 respiratory symptoms. The risk of having respiratory symptoms increased 47%-94% in overweight schoolchildren. Watching TV > or = 3 hrs/day was associated with more occurrences of respiratory symptoms (aOR = 1.42-1.90). Physical activity > or =3 times/week was associated with fewer occurrences of respiratory symptoms (aOR = 0.66-0.73). Overweight was positively associated with an increased risk of suspected asthma in boys (aOR = 1.56, 95% CI = 1.07-2.29), but not in girls. In summary, overweight and greater TV-watching time increase the risk of respiratory symptoms, while habitual physical activity decreases the risk of respiratory symptoms. Weight status, sedentary life, and frequency of physical exercise are the factors that can impact on the respiratory health of schoolchildren.