Data concerning final height (FH) in isolated growth hormone deficiency type 1A (IGHD1A) are scanty and controversial. In this paper we report the FH outcome of two girls with IGHD1A who were treated either with GH only (first patient) or with GH during the first 8 years and successively with IGF-I (second patient). In the first patient, FH was only slightly subnormal and slightly taller with respect to target height (TH). Surprisingly, FH was severely subnormal and very far from TH in the patient who underwent IGF-I therapy for >5 years: an auxological outcome similar to the one recently reported in the only two cases in the literature of patients with IGHD1A who have been treated with IGF-I until near FH achievement. We conclude that IGHD1A could have a very heterogeneous phenotypic expression in terms of FH and that IGF-I therapy, even though initiated some years before puberty onset and prolonged for more than 5 years, may not be able to ensure the normalization of height prognosis and the achievement of an FH close to TH.