Clenbuterol was investigated as a potential marker of baits for the oral vaccination of dogs (Canis familiaris) against rabies in Turkey. Orally administered clenbuterol is incorporated into the hair fibre during hair growth, and the uptake of clenbuterol into the hair of 18 dogs was therefore investigated in a controlled laboratory experiment. Clenbuterol could be detected in the hair of the dogs 28 and 56 days after they had eaten a bait containing 0.5 mg clenbuterol. In a field study, 150 baits containing clenbuterol were distributed at selected sites along roads in the suburban areas of Ferhatpasa, Istanbul; the baits incorporated a vaccine container with the live modified rabies virus vaccine SAD Bi9. By the following morning, 93 per cent of the baits had gone. Hair samples from nine of 31 recaptured dogs contained more than 1 ng clenbuterollg, indicating that they had consumed a bait. However, only four of the 31 dogs had an increased antibody titre. The results of this field study indicate that the placing of baits at selected sites is not a very efficient method of vaccinating ownerless dogs.