We present a case of a 16-year-old girl, who attended the Endocrinology Outpatient Clinic of the University Paediatric Hospital in Kraków, because of lack of breast development and primary amenorrhea. Pubic hair development was normal. Baseline hormonal blood tests indicated a primary gonadal lesion (hypergonadotropic hypogonadism). Ultrasonography examination revealed bilateral streak gonads in ovarian localisation. Uterus was present. The karyotype was male: 46, XY. Gonadectomy was performed due to risk of gonadoblastoma development in streak gonads. Based on the histology of the removed gonads the final diagnosis of complete gonadal dysgenesis 46, XY was established. After the gonadectomy hormonal replacement therapy was introduced. Authors emphasise the importance of considering in each case of delayed puberty in teenage girls the possibility of complete gonad dysgenesis 46, XY. The diagnosis can be established only on the support of a reliable knowledge of male sex differentiation physiology.