We compared final height to height at diagnosis (expressed as a standard deviation score, SDS), predicted adult height (according to the Bayley and Pinneau method) and target genetic height (expressed as mean parental height in cm, +6.5 for males and -6.5 for females) in 37 patients (15 males, 22 females) with insulin-dependent diabetes mellitus (IDDM), aged 20.6 +/- 3.3 years (16.6-27), with 11.8 +/- 3.7 years (5.2-19.2) mean duration of disease. In the 22 females, final height (162.4 +/- 5.7 cm; range, 150-174 cm) was higher than predicted (161.5 +/- 7.8 cm; range, 146-176.2 cm) and target genetic height (159.7 +/- 3.8 cm; range, 152.8-167.3 cm), although not significantly. Female patients showed a positive correlation between final height and both predicted (P < 0.05) and target genetic height (P < 0.005). No difference was observed in final height between patients diagnosed in the prepubertal or pubertal phase (162.2 +/- 4.6 cm vs. 163.4 +/- 6.2 cm; P-value n.s.). In the 15 males, final height (173.4 +/- 4.4 cm; range, 166.5-181 cm), lower than predicted (175.4 +/- 4.9 cm; range, 166-183 cm), was higher than target genetic height (169.9 +/- 4.8 cm; range, 162.4-177 cm) (P < 0.05). Male patients showed a positive correlation between final height and target genetic height (P < 0.05). No difference was found in final height between patients diagnosed in the prepubertal or pubertal phase (173.6 +/- 3.5 cm vs. 172.7 +/- 5.5 cm; P-value n.s.).(ABSTRACT TRUNCATED AT 250 WORDS)