Abstract: Objective To explore the clinical characteristics of nonclassical 21-hydroxylase deficiency (21-OHD) and summarize the experience of diagnosis and treatment to improve the management to the disease. Methods Clinical data about 16 patients with nonclassical 21-OHD in our department in recent years were retrospectively analyzed and related literatures were summarized. Results Totally 16 patients (6 males and 10 females) aged 15-70 years were included.The female patients were presented with irregular menstruation (5/10),hairy and acne (7/10) or primary infertility (5/10),while the other six male patients were presented with skin pigmentation (2/6),sexual precocity (4/6),sterile (1/6),or asymptomatic (1/6).Average plasma ACTH level was (20.91±8.01) pmol/L,and serum 17-OHP level was (16.49±12.17) ng/ml in female and (16.25±5.31) ng/ml in male.Medium-dose dexamethasone suppression test showed that serum 17-OHP level could be inhibited by more than 50% in all the cases (15/15),and ACTH stimulation test showed that serum 17-OHP level increased to higher than 15 ng/ml (<1.8 ng/ml) in 60 minutes (4/4).CT scan showed bilateral adrenal hyperplasia (7/16),bilateral tubercle (5/16),unilateral adenoma (2/16) or no abnormalities (2/16).Glucocorticoid treatment was delivered to 15 patients.During the follow-up,9 female patients adhered to the treatment,and the menstruation returned to normal. Conclusion In female patients with hyperandrogenemia and male patients with precocious puberty or adult infertility,differential diagnosis of nonclassical 21-OHD should be emphasized.Glucocorticoid replacement therapy can improve the prognosis of this disorder.