Fifty nine boys and 41 girls underwent exercise stress testing (ETT), utilizing the Bruce protocol. Their mean age was 10 years. They were grouped by sex, age and body surface area. Blood pressure (BP), heart rate (HR) at rest, during exercise and after were monitored as well as the duration of the test and the energy cost. The HR and-BP had a similar linear relationship in both groups during the different stages of the test. The duration of the test expressed in minutes was 11.8 +/- 1.2 in boys and 10.7 +/- 1.2 in girls (P = 0.001). The oxygen consumption (ML/kg/min) was 45.2 +/- 4.9 and 41.9 +/- 4.5 that is equivalent to 12.9 +/- 1.4 and 11.9 +/- 1.2 mets for each group respectively. The group of boys of 6 (9.8) and 14 years of age (13.6) (P = 0.002) and in the girls in the 7 (9.5) and 10 years age group (11.8) P = 0.05. We conclude that 1) The ETT can be done in children safely but was have to take in consideration their age, sex, and body surface area in evaluating the results. 2) This study gives a reference to evaluate children with an without heart disease.