The Kids' Inpatient Database, reflecting 6.70 million pediatric discharges in 1997 and 7.30 million in 2000, was coupled with the US Census Bureau data and was used to elicit the epidemiology of idiopathic slipped capital femoral epiphysis (SCFE) that occurred in children 9-16 years. It was found that the overall incidence of SCFE in the United States for these years was 10.80 cases/100,000 children. The relative incidence of SCFE was 3.94 times higher in black children and 2.53 times higher in Hispanic children than in white children. The incidence rate was significantly higher in boys (13.35 cases/100,000 children) than in girls (8.07 cases/100,000 children). Higher incidence rates of SCFE were found in the Northeast and West when compared with rates in the Midwest and the South, suggesting that climate plays a role in the onset of SCFE. Increased incidence of SCFE was noted north of 40 degrees latitude during the summer and south of 40 degrees latitude during the winter. Age of onset was also lower than previously reported and seems to be on a downward trend. This study suggests that the relative incidences of SCFE in blacks and Hispanics are higher than previously reported in the United States. Geographic, racial, and seasonal variations suggest that both environmental and genetic factors may influence the development of SCFE.