I-labelled testosterone was prepared with a new klnd of bridge.The product was 125I-testosterone-3-（p-hydroxyphenylacetyl）hydrazone.To-3-HPAH was synthesized in three steps

identified by IR

NMR

MS and ultimate analysis

and then labelled with Na125Iby the chloramine-T method. The yield was higer than 85%.The radiochemical purity was higher than 95%when the product was purified by chloroform extraction and dropped slightly after a 50 days′storage at room temperature