Male pseudohermaphroditism is a condition of sex differentiation disorders in which the gonads are tests, but the genital ducts and/or external genitalia are incompletely masculinized. This syndrome is caused by a failure of the sequential process in embryonal development of the testis. In the presence of functioning testis the Müllerian ducts regress, while the mesonephric ducts and urogenital sinus differentiate into the internal and external male genitalia. Male pseudohermaphroditism is classified to subtypes according to etiological factors: (1) testicular unresponsiveness to hCG and LH; (2) defect in testosterone biosynthesis; (3) end-organ resistance to androgen; (4) defects in the intracellular metabolism of testosterone; (5) aberrations in testicular organogenesis; (6) defects in anti-Müllerian hormone.