AbstractBy using iodine‐131 prepared in the radioisotope laboratory of the National Tsing Hua University, a systematic study was carried out to prepare iodine‐131 labelled human serum albumin (RISA) for domestic use as a radiopharmaceutical. Special emphasis was placed on the purification of RISA in an attempt to meet the specifications required by medical workers. The optimum conditions for radioiodination reaction and purification procedure are discussed in details. It was concluded that the RISA prepared in the Tsing Hua Laboratory is acceptable for radiopharmaceutical