Text: Studying Klinefelter syndrome (47,XXY), a genetically defined disorder characterized by the presence of an additional X chromosome, can reveal insights into genotype-phenotype associations. Klinefelter's syndrome is the most common genetic cause of human male infertility, but many cases remain undiagnosed because of substantial variation in clinical presentation and insufficient professional awareness of the syndrome itself. Early recognition and hormonal treatment of the disorder can substantially impro ve quality of life and prevent serious consequences. However, nowadays patients with Klinefelter's syndrome, including the non-mosaic type, need no longer be considered irrevocably infertile. Cytogenetic analysis were performed by standart methods. For each case at least 25 metaphases were evaluated.. Cytogenetic analysis were performed for 2695 infertile men and among 28 chromosomal abnormalities found, twenty were compatible with Klinefelter's syndrome. Nineteen Klinefelter's patients showed a non-mosaic 47,XXY and one showed a 47,XXY/46,XY, Yqh(+) mosaic by G banding analysis of 20 cells. In eight cases (0.29%), chromosomal aberrations were detected as three 46,XY,inv(9) (0.11%), one 45,X, +marY (0.03%), three 46,XY, Yqh(+) and 46,XY, del (1) (0.03%). In order to assess the frequency of chromosomal abnormalities in azoospermic males from Elazig Turkey, we carried out a retrospective study in 2695 patients. Eight (0.29%) cases with an abnormal karyotype were found. The most frequen t chromosomal anomaly was 47,XXY, which was identified in 20 subjects (0.75%). We suggest that karyotyping is needed in evaluating males for genetic counseling and chromosomal diagnosis.