A female infant with partial trisomy 10 mosaicism and hypomelanosis of Ito is presented. Features include a prominent forehead, hypertelorism, large dysplastic ears, prominent nasal root, a cleft lip and alveolar ridge, bilateral metatarsus adductus, and streaks and whorls of hypopigmented skin. The skin findings were diagnostic for hypomelanosis of Ito. A peripheral blood karyotype was normal. Fibroblasts from a junctional skin biopsy revealed mosaicism for partial trisomy of chromosome 10 [46, XX/47, XX, +del(10) (q11.2q23.2)]. The physical findings of this patient are compared to five published cases of complete trisomy 10 mosaicism and 94 cases of isolated trisomy 10p and trisomy 10q.