Objective: To expose the role of ultrasound and ultrasound markers for detecting chromosomal defects. Especially to underline nuchal translucency as most powerful marker from six years experience. Material and methods: From august 2000, as a certified sonographer from Fetal Medicine Foundation-London UK, I included nuchal translucencies as a standard in screening for chromosomal defects .Examinations were performed on several machines( Siemens Versa Pro, ATL 5000, Voluson 730 Expert) . All data were saved in Astaria Calculation software for chromosomal defects. This software is personalized for all certified sonographers from Fetal Medicine Foundation. Under instructions from FMF, the most significant time for screening is between 11+0 and 13+6 gestational weeks. Results: From August 2000 to May 2006 were examined 460 patients. Measurements of nuchal translucency were: < 5 percentile < median > median > 95 >99 percentile 2.9 % 58.5 % 43.5 % 2.9% 0.6% 86(18.8 %) from the examined patient were over 35 years. Risk for chromosomal aberrations 1:300 and more were calculated in 20(4.4%) of patients. These patients are in group of screen positive. All of them were offered amniocentesis. From kariotipizied patients were identified 2 cases with Trysomy 21, 1 with Trysomy 18, 2 with Trysomy 13 and one case with Turner SY. Conclusion: Ultrasound markers in last 15 years are most significant noninvasive tool in detection of chromosomal abnormalities. Despite Nuchal translucency as most powerful there are 8-10 other ultrasound markers (plexus chorioideus cists, abdominal wall defects, pyelectasis, cardiac defects, short femur etc.). Author incorporated in routine examinations, nuchal translucency from august 2000. In the past years, as routine examination is nasal bone measurement as another very significant marker. Our results are very close to those from world centers. Our results are a small confirmation that ultrasound markers, especially in first trimester, are strong tool in detection and prevention of chromosomal defects and structural abnormalities.