Monozygotic twins with Turner syndrome have rarely been reported. An increased incidence of slipped capital femoral epiphysis has been associated with growth hormone therapy, as well as with Turner syndrome, but has never been described in twins with Turner syndrome. We report the first case of monozygotic twins with Turner syndrome with a 46,Xi(Xq) karyotype, both of whom developed slipped capital femoral epiphysis during growth hormone therapy. This report adds to existing reports of monozygotic twins with Turner syndrome and contributes to recognition of the potential clinical course in such patients. In addition, the association between slipped capital femoral epiphysis, growth hormone therapy, and Turner syndrome is emphasized.