Obesity is thought to be an aetiological factor for slipped capital femoral epiphysis (SCFE). We analysed changes in the incidence of SCFE in Scotland over the last two decades. During this period rates of childhood obesity have risen substantially and evidence for a relationship between these changes and the incidence of SCFE was sought. We found that the incidence of SCFE increased from 3.78 per 100,000 children in 1981 to 9.66 per 100,000 in 2000 (R(2) = 0.715): a two and a half times increase over two decades. It was seen at a younger age, with a fall in the mean age at diagnosis from 13.4 to 12.6 years for boys (p = 0.007) and 12.2 to 11.6 for girls (p = 0.047). More children under eight years old were seen with SCFE in Scotland in the decade to 2000 than in the previous decade (p = 0.002, R(2) = 0.346). A close correlation was observed between rising childhood obesity over the last 20 years in Scotland and an increasing incidence of SCFE.