: media-1vid110.1542/5828355774001PEDS-VA_2018-1067Video Abstract BACKGROUND: Slipped capital femoral epiphysis (SCFE) is believed to be associated with childhood obesity, although the strength of the association is unknown. METHODS:We performed a cohort study using routine data from health screening examinations at primary school entry (5-6 years old) in Scotland, linked to a nationwide hospital admissions database. A subgroup had a further screening examination at primary school exit (11-12 years old). RESULTS:BMI was available for 597 017 children at 5 to 6 years old in school and 39 468 at 11 to 12 years old. There were 4.26 million child-years at risk for SCFE. Among children with obesity at 5 to 6 years old, 75% remained obese at 11 to 12 years old. There was a strong biological gradient between childhood BMI at 5 to 6 years old and SCFE, with the risk of disease increasing by a factor of 1.7 (95% confidence interval [CI] 1.5-1.9) for each integer increase in BMI z score. The risk of SCFE was almost negligible among children with the lowest BMI. Those with severe obesity at 5 to 6 years old had 5.9 times greater risk of SCFE (95% CI 3.9-9.0) compared with those with a normal BMI; those with severe obesity at 11 to 12 years had 17.0 times the risk of SCFE (95% CI 5.9-49.0). CONCLUSIONS:High childhood BMI is strongly associated with SCFE. The magnitude of the association, temporal relationship, and dose response added to the plausible mechanism offer the strongest evidence available to support a causal association.