X-linked hypophosphatemia, the most common form of familial rickets, is conventionally treated with 1,25-dihydroxyvitamin D3 (5-50 ng/kg per day) plus phosphate supplementation (70-100 mg/kg per day). However, nephrocalcinosis is noted in many children treated with this therapy. Whether to treat or not and whether such treatment should be continued into adulthood or in pregnancy are unsettled questions. This article reviews these controversies and provides current recommendations.