This paper reports the preparation of deuterium and tritium labelled ST-1435 （19-Nor-16-methylene-17 α-acetoxy-progesterone （Ⅱ）） by decarboxylation of 16-methylene-17α-acetoxy-19-oci acid-pregnen- 4-ene-3

20-dione （Ⅰ） in deuterated or tritiated solvents. Deuterium incorportion rate for m/e 371（M+） was 22.6% as determined by mass spectrometer. The tritiated ST-1435 was obtained with a specific radioactivity of 52.5 TBq/mol and a radiochemical purity of over 95%.