OBJECTIVES: To determine: 1) the response or cure rate of hyperthyroidism to fixed doses of 370MBq (10mCi) and 555MBq (15mCi) Radioactive Iodine (RAI) therapy, and 2) the incidence of hypothyroidism at 6months post RAI therapy. METHODS: A retrospective review of the records of 20 hyperthyroid patients treated with radioiodine to determine response rate of hyperthyroidism to two fixed dose regimens of RAI therapy was carried out. Twelve (12) and 8 patients received 370MBq (10mCi) and 555MBq (15mCi) fixed dose regimens respectively. The data on demographic (age, gender), clinical (presence of eye disease, the size/type of goiter) and biochemical variables (serum Thyroid Stimulating Hormone -TSH) were obtained. Primary outcome is to cure hyperthyroidism by rendering the patient either euthyroid or hypothyroid within 6months of single dose RAI therapy.  Statistical analysis was carried out with SPSS version 15.0 and the level of statistical significance was taken as P <0.05. RESULTS: Three (3) males (15%) and 17 females (85%) received RAI therapy for Graves’ hyperthyroidism. Their mean age was 49.4 years (range of 25-75years). Fixed doses of 370MBq (10mCi) and 555MBq (15mCi) both produced a response or cure rate of 100%. Overall, 65% and 35% were made hypothyroid (TSH>6.1mIU/L) and euthyroid (TSH=0.21-6.0mIU/L) respectively. The incidence of hypothyroidism was 66.6% with fixed dose of 370MBq (10mCi) and 62.5% with fixed dose of 555MBq (15mCi) within 6months post RAI therapy. There was no significant difference in the incidence of hypothyroidism produced by the two fixed doses of RAI therapy. CONCLUSIONS: Radioactive iodine at fixed doses of 370MBq (10mCi) and 555MBq (15mCi) was highly effective for the treatment of Graves’ hyperthyroidism, with a cure rate of 100%. Fixed doses of 370MBq (10mCi) and 555MBq (15mCi) produced incidences of hypothyroidism of 66.6% and 62.5% respectively within 6 months of RAI therapy which are not statistically different.