The large amount of iodine-131 (131 I) activity excreted by the patient via perspiration, saliva, breath and urine during hospitalization may develop radiation contamination hazard. The aim of this study was to measure the level of contamination activity from skin and room surfaces throughout radioiodine ablation patient's hospitalization and to determine the correlation between the administrated dose and level of contamination activity from skin and room surfaces. The removable activity was measured from nine patients treated with radioactive 131 I with doses ranged from 3.0 to 5.5 GBq (80-200 mCi). The measurement was made at patient's skin and room surfaces in the three-time interval of 4, 10 and 24 hours. The results showed that the removable activity for skin and room surfaces exceeds the regulation level for most of the time post 131 I administration throughout patient's hospitalizations. There was no significant correlation between levels of surface contamination and treatment dose received by the patient. The radiation safety precautions must be considered in order to minimize radiation exposure to the family, personnel and community either during hospitalization or after discharge.