['Birth weight influences both postnatal growth and the initial response to GH therapy in GH-deficient subjects, but its relationship to final height is uncertain. Therefore, we examined final height results in a group of subjects treated for GH deficiency who were born small, appropriate or large for gestational age (GA).', 'Retrospective study.', '108 GH-treated patients (age at diagnosis 11.1 +/- 2.0 years) affected by idiopathic and isolated GH deficiency (peak < 8 microg/l after pharmacological and/or nocturnal mean GH concentration </= 3.3 microg/l) were examined. Twenty-four had a birth weight < 3rd centile (2300 g +/- 268 - small for GA), 77 between the 3rd and 90th centile (3216 g +/- 317: appropriate for GA) and 7 above the 90th centile (4193 g +/- 143: large for GA).', 'All subjects reached final height (growth velocity < 0.5 cm/year in the last year of treatment) after hGH treatment (range 33-96 months) at a dose of 20 U/m2/week. The 3 groups of subjects started therapy at a similar height for chronological and bone age.', 'Final height in the small for GA group was - 1.71 +/- 0.93 standard deviation score (SDS), significantly lower than that of both appropriate (- 1.14 +/- 0.83 (P < 0.01)) and large (- 0.70 +/- 0.89 (P < 0.01)) for GA groups. Similarly, the small for GA group had a significantly lower height SDS increment from the start of therapy to adult height (0.54 +/- 0.84) than both the appropriate (0.99 +/- 0.78 (P < 0.05)) and the large (1.49 +/- 0.84 (P < 0.01)) for GA groups. The percentage of subjects with final height above target height was significantly different in the 3 groups: 21% for the small, 38% for the appropriate and 71% for the large for GA groups (P < 0.05). In the whole group of patients there was a positive correlation between birth weight and final height (r = 0.38; P < 0.0001).'] Does birth weight affect final height in patients treated for growth hormone deficiency?