AbstractTritium labelled cyclohexene oxide, trans‐stilbene oxide and phenanthrene 9,10‐oxide were prepared with specific activities of 0.7 ‐ 1.1 mCi per mmole starting with monoor diketo compounds.Tritium was introduced by reducing the ketone precursors with tritiated complex metal hydrides.The resulting alcohols were transformed to the epoxides by methods described for the unlabelled compounds.The syntheses require only two or three steps and yield cyclohexene oxide, trans‐stilbene oxide and phenanthrene 9,10‐oxide, important substrates for the study of epoxide hydratase and glutathione S‐transferases in high radiochem