A cephalometric study was performed in 19 patients with Turner's syndrome, aged 8.7-16.5 years. A lateral roentgencephalogram was taken before and after two years of treatment with biosynthetic growth hormone in a dose of 24 IU/m2/week. During two years of growth hormone treatment, the mandibular length increased mainly due to vertical growth. The initially posteriorly rotated mandible showed an anterior rotation, although the normal position was not reached. The other linear measurements and angles did not change during treatment. No indications were found for an increase in the disproportionate growth or for excessive chin growth as a sign of acromegaly during growth hormone treatment. In conclusion, growth hormone treatment in patients with Turner's syndrome resulted in an increase in mandibular length, mainly due to vertical growth of the ramus and in the anterior rotation of the mandible