Gender is determined by the genetic, gonadal and hormonal/ phenotypic sex. Genetic sex is determined at conception. The establishment of the gonadal sex (ovary/testis) and the phenotypic sex (external and internal genitalia) is a complicated multistep process which is determined during fetal life mainly during the first trimester. Recently more genes have been found to be involved in this process. Prenatal diagnosis of fetal gender can be made using ultrasound technology, genetic and hormonal examinations. Nowadays using a vaginal and abdominal transducer for US examination recognition of external and internal genitalia of both genders is possible. The determination of gender during fetal life is important not only as a matter of curiosity; in some cases of ambiguity (for example congenital adrenal hyperplasia) prenatal treatment can change the natural history of the disease. Prenatal diagnosis can also subtype the ambiguity, and its severity can be established. In this review we describe our experience in prenatal diagnosis and establishment of the fetal gender, the subtypes of ambiguity and our suggestion for the process of diagnostic work-up.