Aim: To assess whether children with Noonan syndrome on long-term growth hormone (GH) therapy improve their final height to near mid-parental height. Methods: Twenty-five prepubertal children (13 girls) with Noonan syndrome (NS) were studied. A single clinician made the diagnosis based on clinical criteria. GH treatment started at an age ranging from 3.1 to 13.8 y and was continued for at least 2 y. Improvement or “ gain” in final height (FH) was defined as either the difference between adult height SD scores (SDS) and pre-treatment height SDS (the childhood component of the Swedish reference) or height SDS compared to the Noonan reference. Results: Ten children received a GH dose of 33 μ g/kg/d (mean age at start 7.7 ± 2.1 y, mean age at stop 17.6 ± 1.7 y) and 15 received a dose of 66 μ g/kg/d(mean age at start 8.6 ± 3.3 y, mean age at stop 18.4 ± 2.1 y). Eighteen out of 25 patients reached FH. A substantial improvement in FH of 1.7 SDS, equivalent to 10.4 cm compared to pre-treatment height, was observed. No significant difference was seen between the two GH doses. Females gained a mean height of 9.8 cm and males 1-13 cm (FH 174.5 ± 7.8 cm vs mean adult height of 162.5 ± 5.4 cm for males with NS) at final height. Moreover, 60% reached a midparental height of ± 1 SD. Conclusion: GH treatment improves final height in patients with Noonan syndrome, with a mean gain of 1.7 SDS. The prepubertal height gain is maintained to final height and the children achieve a height close to their mid-parental height. Aim: To assess whether children with Noonan syndrome on long-term growth hormone (GH) therapy improve their final height to near mid-parental height. Methods: Twenty-five prepubertal children (13 girls) with Noonan syndrome (NS) were studied. A single clinician made the diagnosis based on clinical criteria. GH treatment started at an age ranging from 3.1 to 13.8 y and was continued for at least 2 y. Improvement or “gain” in final height (FH) was defined as either either the difference between Adult height SD scores (SDS) and pre-treatment height SDS (the childhood component of the Swedish reference) or height SDS compared to the Noonan reference. Results: Ten children received a GH dose of 33 μg / kg / d (mean age at start 7.7 ± 2.1 y, mean age at stop 17.6 ± 1.7 y) and 15 received a dose of 66 μg / kg / d (mean age at start 8.6 ± 3.3 y, mean age at stop 18.4 ± 2.1 y). Eighteen out of 25 patients reached FH. A substantial improvement in FH of 1.7 SDS, equivalent to 10.4 cm compared to pre -treatment height, was observed. No significant difference was seen between the two GH doses. Females gained a mean height of 9.8 cm and males 1-13 cm (FH 174.5 ± 7.8 cm vs mean adult height of 162.5 ± 5.4 cm for males with Conclusion: GH treatment improves final height in patients with Noonan syndrome, with a mean gain of 1.7 SDS. The prepubertal height gain was maintained to final height and the children achieve a height close to their mid-parental height.