Objective: Present our 14-year experience in Radioactive iodine-131 (131RAI) therapy in Graves`s disease (GD) and toxic adenoma (TA). Methods: 525 patients were included, 445 were having GD and 80 TA. one hundred ninety-nine patients received first dose ranging from 296- 444 MBq and 326 received dose ranging from 555- 1073 MBq. Results: Among 525 patients, 368 (70.1%) recovered, out of them 66.3% patients with GD and 91.3% patients with TA, with a statistically significant difference in cure rate between both groups in favor of the latter (P <0.001). Higher doses had higher cure rate in GD (75.5% vs. 50.3%, P<0.001), however no difference in cure rate between higher and lower doses was found TA (93.2% vs. 88.9%, P=0.69). In GD; male gender, presence of ophtalmopathy, moderate & large sized glands, absence of old thyroidectomy, higher Tc99m uptake and lower 131RAI were less likely to be cured , in TA, less response was found in higher thyroid uptake & TSH values. In multivariate analysis; medium & large sized glands and higher Tc99m thyroid uptake values were found to be an independent variables that reduce response in GD while only higher thyroid uptake value was found to be an independent variable that adversely affects response in TA. The second therapy dose controlled the remaining seven patients who had TA with 100 response rate, while achieving 87.3% response rate in GD patients. The remaining uncontrolled nineteen GD patients required two more additional doses. Conclusion: 131RAI is successful after two doses, however some patients may need up to four doses. Higher first dose is recommended for those who expect to have lower cure rate such as who had medium & large sized glands in GD and higher Tc99m thyroid uptake in GD & TA, but this is not necessary in the second dose