Introduction: Down syndrome (DS) (trisomy 21) is the most frequent chromosomal cause of mental retardation, with a frequency rate of about 1 in 700 births. The prevalence of epilepsy in subjects with DS is reported to range from 1% to 13%, higher than in the general population but lower than in patients with mental retardation. Aim: To find the prevalence of convulsion in Down syndrome patients attending pediatric hospital at Benghazi and to find the associated factors related to convulsion in Down syndrome patients. Methodology: cross –sectional study included all Down syndrome patients admitted to pediatric hospital during two years period ( 2020- 2021) , and Patients attending both genetic and neurological clinics during the same years. Results: Total number of cases was 150; History of convulsion was positive in (18)12% of Down syndrome patients. Majority (89%) of patients had generalized tonic clonic, 5.5% had focal convulsion, and 5.5 % had infantile spasm, all patients were in treatment and had good response. Males constitute to 61% of all patients with male to female ratio 1.6:1. Nearly half (50.4%) of male patients their age was 1- 5years, while 43.8% of females was in same age group. Majority of mothers age were > 32years, 88% of all mothers their age 30years or above. All patients with convulsion had no complication during delivery, while 9% of patients without convulsion had complications. More than half (61.5%) of the patients the convulsion started before the age of one year. Results of EEG were abnormal in 25% of patients with convulsion. Conclusion: Normal ECHO was found in 33% of all cases, Atrial septal defect was recorded in 27% of patients with convulsion and 19.5% of patients without convulsion, Ventricular septal defect and Atrial septal defect in 15.4% of patients with convulsion and 10.3% of patients without convulsion, Patent ductus arterious was in 11.5% of patients with convulsion and 3.2%of patients without convulsion. More than .........