<i>Background:</i> The potential involvement of <i>SRY</i> in abnormal gonadal development in 45,X/46,X,der(Y) patients was proposed following the identification of <i>SRY</i> mutations in a few patients with Turner syndrome (TS). However, its exact etiological role in gonadal dysgenesis in patients with Y chromosome mosaicisms has not yet been clarified. <i>Aims:</i> It was the aim of this study to screen for allelic variation in<i> SRY</i> in a large cohort of patients with disorders of sex development due to chromosomal abnormalities with 45,X/46,X,der(Y) karyotype. <i>Patients:</i> Twenty-seven patients, 14 with TS and 13 with mixed gonadal dysgenesis (MGD), harboring 45,X/46,X,der(Y) karyotypes were selected. <i>Methods:</i> Genomic DNA was extracted from peripheral blood leukocytes of all patients and from gonadal tissue in 4 cases. The <i>SRY</i> coding region was PCR amplified and sequenced. <i>Results:</i> We identified only 1 polymorphism (c.561C→T) in a 45,X/46,XY MGD patient, which was detected in blood and in gonadal tissue. <i>Conclusion:</i> Our results indicate that mutations in <i>SRY</i> are rare findings in patients with Y chromosome mosaicisms. Therefore, a significant role of mutated <i>SRY</i> in the etiology of gonadal dysgenesis in patients harboring 45,X/46,XY karyotype and variants seems very unlikely.