The changes in body composition evaluated by the mean of bioelectrical impedance analysis (BIA) have been observed in a group of 16 male adolescents at the time of discontinuation of growth hormone (GH) therapy as well as at 6 and 12 weeks later. After reevaluation of their endocrine function, 6 patients (3 craniopharyngioma, 1 irradiation, 1 malformative, 1 idiopathic) had a profound persistent GH deficiency (maximum peak of GH under provocative tests < 5 ng/ml and low IGF-1 levels), while 10 patients had a normal somatotropic function. Both groups were comparable as far as age, weight and body mass index are concerned. Fat weight is significantly higher in the GH-deficient patients (9.9 +/- 2.6 kg) than in boys with a normal somatotropic function (6.0 +/- 1.1 kg) at the time of the discontinuation of GH therapy (p < 0.01). 3 months later, the increase in fat weight is significant only in the group of patients with severe GH deficiency (+4.1 +/- 2.2 kg; p < 0.05), the difference between the 2 groups (14.0 +/- 3.5 and 7.3 +/- 1.0 kg) becoming highly significant (p < 0.001). Lean body mass is lower in the GH-deficient patients and decreases slightly after GH discontinuation, while no significant variation is observed in the group of non GH-deficient boys. Although BIA assessment of body composition may be discussed when applied to GH-deficient subjects, these results show that such patients should be reevaluated after the discontinuation of GH therapy, including examination of the possible metabolic consequences of GH deficiency.