Three postpubertal males 17-19 yrs old, 2 with 21-OH and one with 11-OH deficiency (def) had testicular nodules. In the patients with 21-OH def, 17 KS were 51 and 21, pregnantriol (p-triol) 41 and 16 mg/24 hr and plasma progesterone (P) 1400 and 1363 ng/dl indicating non-compliance; plasma testosterone (T) were 973 and 1245 ng/dl and LH and FSH < 3.6 and 1.5 mIU/ml. One patient examined had azoospermia. After 5 days of dexamethasone (Dex) urinary 17 KS and p-triol were suppressed, plasma P fell to 58 and 60 and T fell to 468 and 358 ng/dl. Plasma LH and FSH rose to adult levels. The sperm count rose to 20 mil. In the patient with 11-OH def urinary 17 KS and comp “S” were 9.0 and 2.8 mg/24 hr and plasma LH, FSH and T were 8.3, 5.4 and 749 respectively. After Dex urinary 17 KS, comp “S” and plasma LH, FSH, and T were 7.8, < 1.0 and 11, 5 and 520. The sperm count was 56 mil before and 25 mil after Dex. Nodules size did not change after Dex. Biopsies of the nodules revealed interstitial cell hyperplasia, and that of the adjacent testis maturation arrest with decreased number of spermatozoa in the 21-OH def patients and mild germ cell def in the 11-OH def patient.The data suggest that in CAH: 1) Continuous stimulation by ACTH can produce adenomatous hyperplasia of Leydig cells 2) LH-FSH suppression results from elevated adrenal T and 3) germ cell hypoplasia and decreased spermatogenesis could result from diminished LH-FSH and subnormal intratesticular T level.