[en] The epimeric gibberellin-A₃-7-aldehydes 1 and 2 were silylated, enolised with KH and labelled with ³H₂O to give after desilylation the tritium-labelled epimeric gibberellin-A₃-7-aldehydes 4 and 5. Subsequent acetylation, oxidation and deacetylation afforded [6-³H] gibberellin-A₃ (6) and [6-³H]6-epi-gibberellin-A₃ (7). Thus, this route provides a convenient method for the preparation of [6-³H]GA₃ of high specific radioactivity. (author)