Background:The management of hyperthyroidism with radioiodineis a standard method andrnhas resulted to be effective with few post therapy complication and recurrencernrate.Objective:To assess the success rate of rn 131rnI treatment in patients with hyperthyroidism,rnwho were registered and under follow up in TikurAnbessa specialized hospital, nuclearrnmedicine unit, college of health Sciences, Addis Ababa University, from 2009-2014. rnMethods:Retrospective study, using quantitative data collection method was conducted for arnperiod of 5 months.A total of 88 patients were found eligible for this study.The therapeuticrndoses were low and highfixed doses. The data was collected in excel spread sheet andrnexported to a software SPSS version 25 for process and analysis.Descriptive statistics werernused to summarize the socio-demographic profiles, pre- and post-therapy TFT results tornevaluate the bio-chemical response, clinical assessment records, and rn99mrnTc-pertechnitaternuptake results. rnResult: Among 88 patients, the age ranges from 18 to 79 years old; the mean age is 44.86,rnfemale to male ratio is 4.2:1. 100% of the patients received ATDs before RAI therapy, among rnthem 4.5% additionally underwent partial thyroidectomy. In the study population, thernproportions of types of hyperthyroidism:- Toxic adenoma -39.8% ,TMNG-37.5% and GD22.7%.rnThernhighestrnresponserndurationrnwasrnachievedrninrn1-6monthsrnbyrn82.95%,rnin7-12rnmonthsrnrnby5.7%rnrnand the least response>12 months-2.3%.General response 90.9% and failure9.1%.Amongrnrnthe failed group post RAI recurrent hyperthyroidism covered 3.4%.Inrndetermining the success rate of RAI in treatment of hyperthyroidism using linear regressionrnanalysis,RAIdose was significant in P-value=0.034, which is