Two unrelated patients with severe short stature (initial heights -7.9 and-6.0 SD), lack of GH response to 2 stimulation tests, were homozygous for a 6.7 kb deletion of the GH-1 gene (demonstrated by PCR) Both have been treated with GH with partial and transitory response due to the development of high titer anti-GH antibodies (even using 1/10 of the usual dose to attempt desensitization). Recombinant IGF-1 (Igef®, Pharmacia, Sweden) was started at a dose of 40 mcg/kg/dose, sc, 30 min after breakfast and dinner, daily. Before IGF-1 therapy, patient 1 was a prepubertal girl with chronological age(CA) of 10.4 years (y), height age (HA) 3.4 y, bone age (BA) 9 y, height 99.5 cm (-6.7 SD), weight 25 kg and growth velocity (GV) without treatment of 4.5 cm/y. Patient 2 was a prepubertal boy with CA 8.8 y, HA 3.2 y, height 98.3 cm(-5.7 SD), weight 19.5 kg and a pre-treatment GV of 1.8 cm/y. During the first year of lGF-I therapy, GV in patient 1 was 11.4 cm/y (1st quarter), 7.5 cm/y(2nd quarter), 7.4 cm/y (3rd quarter) and 3.6 cm/y (4th quarter) when she started puberty. In patient 2, GV was 8.5 cm/y (1st quarter) and 6.4 cm/y (2nd quarter), when the IGF-I was increased to 60 mcg/kg/dose and GV was 7.8 cm/y(3rd quarter) and 3.9 cm/y (4th quarter). Side effects like hypoglycemia, hypokalemia, postural hypotension, headaches, tachycardia or intracranial hypertension did not occur We conclude that therapy with recombinant IGF-I, 40-60 mcg/Kg, twice a day, during one year, improved significantly GV in 2 patients with GH gene deletions. without side effects. The efficacy for longer periods of time remains to the established.