To evaluate the effect of growth hormone treatment on final height, phosphate metabolism, bone markers, and bone mineral density in children with X-linked hypophosphatemic rickets. Six patients (aged 7.8 +/- 1.8 years; height z score, -3.4 +/- 0.5) received conventional treatment (1,25-dihydroxyvitamin D(3) plus phosphate salts) combined with growth hormone (0.6-0.9 IU/kg per week, subcutaneously) (group A); 6 patients (aged 7.9 +/- 2.5 years; height z score, -2.1 +/- 0.6, P <.01 with respect to group A) received only conventional treatment (group B). Final height z score significantly improved in group A (-2.4 +/- 0.5, P <.03 with respect to the value at entry), whereas it did not change in group B (-2.8 +/- 0.5, P = NS). At final height, degree of body disproportion was similar between the groups (group A, 1.3 +/- 0.2; group B, 1.2 +/- 0.1; P = NS). Phosphate retention, bone markers, and radial bone mineral density increased only in group A. No adverse effects were observed. In poorly growing patients with X-linked hypophosphatemic rickets, growth hormone therapy combined with conventional treatment improves final height, phosphate retention, and radial bone mineral density, but it does not influence degree of body disproportion.