Mixed gonadal dysgenesis includes a heterogenous group of different chromosomal, gonadal and phenotypic abnormalities characterized by the presence of a testis on one side and a streak or absent gonad on the other, persistence of Mullerian duct structures and a variable degree of genital ambiguity. These patients are chromatin negative and exhibit XO/XY mosaicism with a high incidence of gonadal neoplastic transformation. Herein, a case of mixed gonadal digenesis is presented, and the literature is reviewed.