Analysis of the SRY gene in a girl with 45,X/46,XY genotype: We present a Turner syndrome patient with a 45, X/46, XY mosaicism. A seven years-old patient was admitted to our laboratory for evaluation of Turner Syndrome. On physical examination, short stature, a webbed neck, a broad chest with widely spaced nipples, syndactyly on toes, horse shoe kidney and typical findings of aortic coarctation were present, The chromosome karyotype of the patient was 45 X/46 XY. Molecular analysis of the blood lymphocytes confirmed the presence of the SRY gene of the patient. We report here the clinical and cytogenetic findings in a patient with an unusual sex chromosome mosaicism.