We report four cases of nonclassical 21-hydroxylase deficiency (21-OHD) diagnosed in neonate or early childhood. The four patients comprised a 6-year, 5-month-old male (case 1); a 3-year, 10-month-old female (case 2); a 13-year, 11-month-old female (case 3) and a 17-year, 1-month-old male (case 4). Cases 3 and 4 were siblings. None had any signs of virilization or salt wasting at birth. 21-OHD was diagnosed using ACTH loading test and other adrenal steroid evaluations. Mutations of the CYP21 gene were detected in all patients. Three patients (cases 1, 3 and 4) had positive results in neonatal mass screening. Cases 1 and 2 showed no apparent signs of virilization and were observed without conventional treatment. In cases 3 and 4, because of increased growth velocity and accelerated bone maturation, hydrocortisone administration was initiated from their late infantile period. In spite of hydrocortisone treatment, in case 4, the final height of 159.7 cm was less than his predicted final height. Besides he revealed adrenal insufficiency at the age of 9 years and 2 months old caused by viral infection. Hydrocortisone supplementation therapy may cause adrenal insufficiency in nonclassical patients due to suppression of the hypothalamus-pituitary-adrenal axis. The clinical courses in these cases were various, and it was difficult to predict the appearance of any symptoms of virilization. Careful observation is necessary.