Summary. Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency is the most frequent cause of genital ambiguity in female newborns. Enzyme deficiency causes a disorder of cortisol synthesis by the adrenal cortex and leads to excessive androgen production resulting in subsequent genital virilization of female fetuses. The incidence of the classical form is 1:10000–15000 live births. About ¾ of affected infants also suffer from a disorder of aldosterone biosynthesis, which can lead to potentially lethal salt-losing crises within the first weeks of life. Here, we report of the case of an unrecognized virilization of a female newborn, who was hospitalized after an adrenal crisis at the twelfth day of life. Supplementary glucocorticoid (hydrocortisone) and mineralocorticoid (fludrocortisone) treatment with the addition of salt led to a fast recovery and satisfactory control of disease during 40 days of hospitalization. The girl was released from the hospital with good prognosis for the future growth and develompent with the recommended ongoing supplementary treatment under the supervision of an endocrinologist.