Final height was evaluated in 47 patients with classical 21-hydroxylase treated since diagnosis, and in 29 patients with nonclassical (NC) 21-hydroxylase deficiency who had never been treated before reaching final adult height. Classical patients achieved final heights consistently below the mean for the general population, and in all but four cases these patients also failed to attain the individual height expectation based on midparental height. Analysis of these results with regard to (1) clinical form (i.e. salt-wasting [SW] or simple virilizing [SV]) and (2) degree of hormonal control (i.e. good or poor) indicates that neither factor seems to affect the height outcome. Final height in NC patients, while significantly greater than for classical patients, was below the general population mean, and individual final heights were also significantly below expectation based on midparental height. In another group of NC patients who were still growing, some of whom were on courses of treatment and some under observation only, height at the time of diagnosis was compared with the most recent height prediction. Reduction of growth potential appeared to be somewhat lessened in the treated group, from which we tentatively suggest that treatment should be considered in NC patients even in the absence of clinical signs of androgenism.