Trisomies occur in the result of ‘'meiotic non-disjunction'' during gametogenesis. In humans, trisomy 21 or Down Syndrome is the best known and the most seen trisomies. Trisomy 21 is one of the most common chromosomal abnormalities with mental retardation and characteristic physical symptoms in humans. In our study, the clinical and cytogenetic analysis were concluded in our center. The cases were sent to our laboratuary for genetic diagnosis because of their clinical features from different centers and it had been performed chromosome analysis from peripheral blood. Of whole cases, 91 (54.4%) were male, 76 (45.5%) were female children, 162 cases of the total (97%) were classic type Down syndrome, 2 cases (41%) were mosaic, 3 cases (17%) were Down Synrome with translocation. Translocation types were t(21;21) in one case and t(14;21) in two cases. The results of the cytogenetic analyses are compatible with the rate of the results in the literature. The median maternal age is 34.04 in this study, the clinical features of the cases with Down syndrome have been also evaluated genetic counseling has been given to all of cases. By the absolute clinical diagnosis, genetic counseling to the family oppositely.