Seventy-eight patients who had constitutional delay of growth and puberty were included in a retrospective study to determine whether, at the time of first evaluation, any predictive features could suggest final height outcome. Mean chronologic age was 14.3 years (range, 12 to 18 years), and all were either prepubertal or in an early stage of pubertal maturation (4 ml testicular volume). Initial mean (+/- SD) height standard deviation score was -2.74 (+/- 0.71); 85% had a relatively short spine compared with subischial leg length. Mean (+/- SD) growth rate was 4.8 (+/- 1.6) cm/year, and epiphyseal maturation was delayed by 2.4 (+/- 1) years. Sixteen boys were treated with a sustained-action preparation of testosterone (50 mg monthly for 3 to 4 months), six with oxandrolone (1.25 mg daily for a mean of 4 months), and one with both drugs in sequence. At final height attainment, 58% of the boys failed to achieve their full genetic potential; among the remaining 42%, only 0.7% attained a final height above corrected mid-parental height. The relative disproportion between the segments had no significant change at final height attainment. Regression analysis showed that final height impairment (the difference between mid-parental height and final height) was negatively influenced by standing height and growth velocity when initially evaluated and positively by the degree of segmental body proportion; that is, patients who were taller, were growing at a faster rate, and who had a major degree of segmental body disproportion with a short spine and long leg length attained a final height closer to their mid-parental height, irrespective of the degree of delayed epiphyseal maturation. Neither testosterone nor oxandrolone administered during early puberty modified final height attainment or segmental proportion. We conclude that a late onset in the timing of puberty seems to be deleterious to spinal growth and consequently to final height attainment. An alternative diagnosis should be sought among patients with features of constitutional delay of growth and puberty who do not have a significant degree of body disproportion. In these patients, as well as in those who are extremely short, who have a poor growth rate, or who have an unfavorable genetic potential, an alternative therapeutic approach may be required.