In this paper we present the first and the largest study on DS patients referred to Medical Genetics Center from different regions and discrete all over Egypt aiming to look for possible causal factors for this high birth rate, and to evaluate the trend of parents and clinicians to the new screening programs and prenatal diagnosis. The study was included 1100 patients referred as DS, 1030 cases were confirmed by cytogenetic analysis to be DS. Most of these cases (98.43 %) were diagnosed postnatally and only 1.56 % were detected prenatally mainly through amniocentesis and rarely products of conception (0.01 %). Their ages ranged from one hour to 30 years with mean of 351 days. Males represented 54.13 % while females represented 45.87 % of the studied group. Mean maternal age at conception was 31.8 years for cases with non- disjunction and 24.5 years for cases with translocation. All mothers of cases of translocation DS were under 35 years, in contrast to mothers of non- disjunction cases in which 41.48 % were above 35. Paternal age ranged from 19 to 62 years with mean of 36.5 years in non-disjunction cases and from 24 - 35 years in translocation cases with mean of 30.6 years. Consanguineous marriage was present in 12 % of cases. Positive family history was present in 6 % of cases. Most of cases were the first or the second in order of birth, and the most common cause of referral was dysmorphic features in live births and advanced maternal age in prenatally referred cases.