BACKGROUND: Recent research has shown that the Fitkids Treadmill Test (FTT) is a valid and reproducible exercise test for the assessment of aerobic exercise capacity in healthy children and adolescents. OBJECTIVE: To provide sex- and age-related normative values for FTT performance in healthy and typically developing children and adolescents aged 6 to 18 years. DESIGN: Cross-sectional, observational study. METHODS: Three-hundred and fifty-six healthy children and adolescents (174 boys and 182 girls; mean ± SD age: 12.9 ± 3.7 years) performed the FTT to their maximal effort to assess time to exhaustion (TTE). The Least Mean Square (LMS) method was used to generate sex-and age-related centile charts (P3, P10, P25, P50, P75, P90, and P97) for TTE attained at the FTT. RESULTS: In boys, the reference curve (P50) showed an almost linear increase with age in TTE from 8.8 minutes at 6 years of age to 16.1 minutes at 18 years of age. In girls, the P50 values for TTE increased from 8.8 minutes at 6 years of age to 12.5 minutes at 18 years of age, with a plateau in TTE starting at approximately 10 years of age. LIMITATIONS: Youth from non-Caucasian origin were underrepresented in this study. CONCLUSION: The current study describes sex- and age-related normative values for FTT performance in healthy, typically developing children and adolescents aged 6 to 18 years. Age- and sex-related normative values will increase the usefulness of the FTT in clinical practice.