Fitness improvement was used to compare morning with afternoon exercise periods for asthmatic children. Children with persistent moderate asthma (according to GINA criteria), 8 to 11 years old, were divided into 3 groups: morning training group (N = 23), afternoon training group (N = 23), and non-training group (N = 23). The program was based on twice a week 90-min sessions for 4 months. We measured the 9-min running distance, resting heart rate and abdominal muscle strength (sit-up number) before and after the training. All children took budesonide, 400 microg/day, and an on demand inhaled ss-agonist. The distance covered in 9 min increased (mean +/- SEM) from 1344 +/- 30 m by 248 +/- 30 m for the morning group, from 1327 +/- 30 m by 162 +/- 20 m for the afternoon group, and from 1310 +/- 20 m by 2 +/- 20 m for the control group (P < 0.05 for the comparison of morning and afternoon groups with the control group by ANOVA and P > 0.05 for morning with afternoon comparison). The reduction of resting heart rate from 83 +/- 1, 85 +/- 2 and 86 +/- 1 bpm was 5.1 +/- 0.8 bpm in the morning group, 4.4 +/- 0.8 bpm in the afternoon group, and -0.2 +/- 0.7 bpm in the control group (P > 0.05 for morning with afternoon comparison and P < 0.05 versus control). The number of sit-ups in the morning, afternoon and control groups increased from 22.0 +/- 1.7, 24.3 +/- 1.4 and 23 +/- 1.1 sit-ups by 9.8 +/- 0.9, 7.7 +/- 1.4, and 1.9 +/- 0.7 sit-ups, respectively (P > 0.05 for morning with afternoon comparison and P < 0.05 versus control). No statistically significant differences were detected between the morning and afternoon groups in terms of physical training of asthmatic children.