The effect of human growth hormone (hGH) on dental structures was investigated by comparing two groups of patients with hypopituitarism. One group of 19 patients with isolated growth hormone deficiency who received hGH replacement therapy was compared with a group of 13 patients with high immunoreactive growth hormone and IGF-I deficiency, Laron-type dwarfism, who could not benefit from hGH treatment. Plaster casts of the dentitions and panoramic radiographs were obtained from all patients and analyzed for dental age, arch length, arch circumference, and width of teeth. the main findings were that (1) hGH therapy did not accelerate dental age but enhanced bone age; (2) the mandible was significantly smaller in the untreated group but no significant difference was found between the groups in the maxilla; (3) third molars were missing in more than 90% of the patients with Laron-type dwarfism whereas hypodontia of other teeth was found in 30% of all the patients; and (4) crowding was less prevalent than expected and the mesiodistal width of the teeth seemed to be smaller.