A 14‐year‐old girl presented with short stature and progressive virilization. She had not undergone the menarche. On investigation, she had elevated testosterone, androstenedione, dihydroepiandrosterone sulphate and 17α‐hydroxyprogesterone levels, which were all suppressed by overnight dexamethasone to within their normal ranges. An initial diagnosis of 21‐hydroxylase deficiency was revised to 11β‐hydroxylase deficiency after a tetracosactrin stimulation test, which showed only a modest rise in 17α‐hydroxyprogesterone level (from 92 nmol/l at baseline to 133 nmol/l at 60 minutes) and measurement of the basal 11‐deoxycortisol, which was grossly elevated. Treatment with dexamethasone 0.5 mg nocte resulted in suppression of androgens in the daytime, but not in the evening, particularly androstenedione. Treatment with hydrocortisone 10 mg b.d. failed to suppress testosterone or androstenedione over a 24‐hour period. Addition of cyproterone and oestrogen supplements had no effect and significant virilization persisted. Laparoscopic bilateral adrenalectomy was therefore performed as definitive treatment and resulted in remarkable clinical and biochemical improvement. This case illustrates difficulties in correct diagnosis, choice of appropriate steroid regimen and monitoring efficacy of treatment in congenital adrenal hyperplasia due to 11β‐hydroxylase deficiency. More aggressive management with earlier bilateral adrenalectomy may be