Two girls with sex-linked hypophosphatemic rickets are described in whom premature fusion of the medial proximal tibial epiphyseal plate exacerbated lower-extremity bowing. Early recognition of this complication and appropriate surgical intervention--excision of the bony bridge in the growth plate, or epiphysiodesis of the still open portion of the growth plate--might prevent further shortening or deformity of the affected limb.