Background/Aims: In some adolescents with constitutional delay of growth and puberty (CDGP), the reduction in relative height (height SDs) starts already in childhood, before puberty. Some subjects with CDGP do not reach their target height (TH). We investigated whether early height SD reduction or testosterone treatment in low doses (1–2 mg/kg/month) influence final height (FH). Methods: The growth of 70 adult men with a history of CDGP was investigated. 31 subjects (13 treated with testosterone) had progressive height SD reduction between 3 and 9 years, and in 39 (17 treated with testosterone) no such reduction was seen. Results: In untreated subjects without early height SD reduction, FH was closer to TH than in those with such reduction (FH – TH 0.05 ± 0.94 vs. –0.63 ± 0.50 SD, p = 0.009). FH – TH did not differ between the testosterone-treated and untreated subjects in the group with early height SD reduction (FH – TH –0.36 ± 0.48 vs. –0.63 ± 0.50 SD, p = 0.15), nor in the group without such reduction (FH – TH –0.08 ± 0.70 vs. 0.05 ± 0.94 SD, p = 0.64). Conclusion: Subjects with early height SD reduction do not attain FH consistent with their genetic height potential, whereas those without such reduction do. Treatment with low doses of testosterone does not adversely affect FH.