Mixed gonadal dysgenesis is a condition characterised by presence of a testis on one side and a streak gonad on the other. Two such patients with the condition are described, one with a predominantly female external genitalia and the other with predominantly male external genitalia. The former was a mosaic of XO deleted Y, while the latter was XY. The majority of individuals with this syndrome have ambiguous external genitalia but with predominantly female genital duct system, and a chromosome constitution of XO / XY. The literature is reviewed and the relationship of the condition with other syndromes of sex abnormalities discussed.