Twelve young African grey parrots with clinical signs of psittacine beak and feather disease (PBFD) virus infection in the UK [date not given] were injected daily with 1 million IU of an alpha type 1 interferon of feline origin (Virbagen Omega) intramuscularly for 90 days. The birds were also fogged with A disinfectant (F10 Super Concentrate) to avoid secondary infections. However, only 2 of the birds survived until week 30 and both were still positive for PBFD virus by polymerase chain reaction (PCR). These birds were then euthanized. Another PBFD virus-positive group of 10 young parrots were treated with 1 million IU avian gamma interferon derived from poultry cell cultures intramuscularly for 90 days. Fogging with F10 was also performed. Seven of the birds survived until week 30 and had increased leukocyte counts. By day 180, all 7 had normal leukocyte counts and were PBFD virus-negative by PCR. These birds were still alive 9 months after initial diagnosis and had not exhibited clinical signs of PBFD infection. In conclusion, gamma interferon of poultry origin has a potential use in the treatment of PBFD virus infection in young grey parrots, while alpha interferon of mammalian origin is not satisfactory for treatment of the disease. No side effects of repeated interferon treatments were observed in any of the parrots.