Background and aim: Reports from several countries suggest that the prevalence and spectrum of the congenital cardiac malformations seen in the setting of Down's syndrome vary in different ethnic groups and countries, and at different periods in the same country. Data on Arab children are lacking. Our study aimed to fill that void by ascertaining the pattern in Omani Arabs. Methods: Prospective clinical and echocardiographic evaluation of consecutively recruited Omani children with Down's syndrome. Results: We studied 110 children, aged from one day to 11 years, with a median of 2 months, detecting 76 cardiovascular malformations in 63 (57%) of them. Atrioventricular septal defect, the most prevalent lesion, accounted for 24 (32%) of the 76 defects. Next were atrial septal defects within the oval fossa (29%), patency of the arterial duct (17%), and ventricular septal defect (14%). There were only two cases of Fallot's tetralogy, one each of coarctation of the aorta and right-sided heart, respectively; and none of discordant ventriculo-arterial connections. Conclusion: The prevalence of cardiovascular malformations is high, at 57%, in our studied population of Arab children. Overall, 92% of the malformations are defects which are characterized by a left-to-right shunt, and the potential for pulmonary hypertension. These findings underscore the need for early detection and prompt, appropriate care. To achieve this, if feasible, all babies born with Down's syndrome should have echocardiography in the first month of life.