Context: A polymorphism in the human GH receptor gene (d3/fl-GHR) resulting in genomic deletion of exon 3 has been associated with the degree of height increase in response to GH therapy. Objective: The objective of the study was to evaluate the frequencies of d3/fl-GHR polymorphism genotypes in control and short small-for-gestational-age (SGA) populations. Design: An adult control population with heights normally distributed (ACPNH) between -2 and +2 SD score (SDS) and a short non-GH-deficient SGA child population were selected. Setting: Thirty Spanish hospitals participated in the selection of the short non-GH-deficient SGA children in the setting of a controlled, randomized trial, and one of these hospitals selected the ACPNH. Controls and Patients: Two hundred eighty-nine adult subjects of both sexes constituted the ACPNH and 247 children and adolescents of both sexes the short SGA patients. Main Outcome Measures: Heights and weights were recorded in the ACPNH, and auxologic and biochemical data were recorded at each hospital for the SGA patients; d3/fl-GHR genotypes were determined and data analyzed in a single hospital. Results: In short SGA patients, d3/fl-GHR genotype frequencies were significantly different from those in ACPNH, with a higher frequency of fl/fl genotype (P < 0.0001). In ACPNH, a trend toward diminished d3/d3 genotype frequency was observed in the shortest height group (height ≤-1 SDS and ≥-2 SDS, n = 60). Conclusions: Our data showed significant differences in the frequency distribution of the d3/fl-GHR genotypes between a normally distributed adult height population and short SGA children, with the biologically less active fl/fl genotype being almost twice as frequent in SGA patients. These data suggest that the d3/fl-GHR polymorphism might be considered among the factors that contribute to the phenotypic expression of growth. Copyright © 2006 by The Endocrine Society.