Xanthohumol (Xn) has well-established chemopreventive potential in vitro. In order to carry out in vivo bioavailability and tissue distribution studies,( 14)C-labelled Xn was produced by biolabelling. Supplying hop sprouts with 5 mCi [U-(14)C]glucose led to incorporation of (14)C into Xn. Delivering the radioactive precursor at once resulted in Xn with a specific activity of 318 microCi.mmol(-1); if however the amount was supplied in aliquots over 4 days a specific activity of only 53.1 microCi.mmol(-1) Xn was obtained.