An outbreak of ornithosis occurred in Lidköping, a small town in Southwest Sweden, in January 1967 through May 1969. 24 proved cases were known, aged from 10 to 72 years, 19 patients gave a history of contact with birds (parrots, canaries, parakeets), 13 of them with birds from the same pet shop. Five patients had visited the pet shop only once before their illness. Attempts to prove infection with ornithosis agent in 7 birds from the pet shop were unsuccessful. Three patients, 2 of them in the same household, had no contact with birds and infection from person to person was strongly suspected. All patients had pneumonia. Fever, cough and headache were predominant clinical symptoms. There were relapses in 4 patients and 2 patients had symptoms of encephalitis. No deaths occurred.