The clinical findings in ten patients with 45,X/46,XY mosaicism are described. Three girls presented with short stature, delayed sexual development or Turner-like stigmata without signs of virilization. Bilaterally gonadoblastomas were found in two girls, and the gonads in one of these girls also contained mucinous cystadenomas. The remaining seven patients were raised as boys. Three had scrotal hypospadias and mixed gonadal dysgenesis. Three presented as male pseudohermaphrodites with scrotal or penoscrotal hypospadias and bilateral testes. One male was diagnosed in adulthood because of gynecomastia, but had normal male external genitals. The clinical findings illustrate the wide spectrum of phenotypic manifestations of 45,X/46,XY mosaicism, ranging from females with Turner-like phenotypes, phenotypic males and females with mixed gonadal dysgenesis, male pseudohermaphroditism to almost phenotypic normal males.