The purpose of this study was to assess the status of and relationship between pulmonary function and physical fitness of children with Down syndrome. Eighteen children, ages 6 to 12 years, with Down syndrome were tested for forced vital capacity (FVC), forced expiratory volume in 1 second (FEV,), forced expiratory flow (FEF25%75%), peak expiratory flow rate (PEFR), and maximum voluntary ventilation (MVV). The Health-Related Physical Fitness Test (HRPFT) assessed levels of cardio-respiratory endurance, abdominal strength, body fat, and flexibility of the low back and hamstrings. Subjects' FVC, FEV, FEF25%-75%, and maximum voluntary ventilation values were significantly lower than values of children without disabilities. Health-Related Physical Fitness Test mean performance scores indicated the subjects were more flexible (56th percentile), had more body fat (37th percentile), and had lower cardio-respiratory endurance and weaker abdominal strength (less than 1st percentile) than the mean scores for age-matched children without disabilities. Significant correlations were found between abdominal strength scores and FVC, FEV, peak expiratory flow rate, and FEF25%-75% values. The findings of reduced pulmonary function and physical fitness measures together with a positive relationship between abdominal strength and pulmonary function in children with Down syndrome suggest potential areas of intervention for physical therapists.