The determination of human adult height is dependent on both environmental and genetic factors. Rare causes of ab- normal stature have been identified, including mutations in the gene encoding aromatase (CYP19) and regions on the Y chromosome. However, the possible role of these loci in the genetic control of normal adult height is unknown. We have performed an association study using common biallelic poly- morphisms within CYP19 and the Y chromosome to determine whether these loci are associated with variation in height in 413 adult males and 335 females drawn at random from a large population sample. An association between CYP19 and height was found (difference, 2.0 cm; 95% confidence interval, 0.16 - 3.8; P 0.003), but this was more evident in men (difference, 2.3 cm; 95% confidence interval, 0.38 - 4.4; P 0.05) than women (difference, 0.2 cm; 95% confidence interval,2.1 to 1.6; P 0.94). An association was also found with the Y chromo- some (P 0.009; difference of 1.9 cm; 95% confidence interval, 0.5-3.4). Additionally, when men were grouped according to haplotypes of the CYP19 and Y chromosome polymorphisms, a difference of 4.2 cm (95% confidence interval, 0.67-7.3) was detected (P 0.004). These results suggest that in men, genetic variation in CYP19 and on the Y chromosome are involved in determining normal adult height, and that these loci may in- teract in an additive fashion. (J Clin Endocrinol Metab 86: 4147- 4150, 2001)