We report three cases of psittacosis in staff working in a veterinary surgery, which was related to exposure to a sick, wild psittacine bird. Chlamydial genus- and chlamydial species-specific DNA was detected in clinical specimens, including throat swabs, whole blood and urine. The organism load was quantified by real-time PCR (RT-PCR), which revealed 10(5)-fold more organisms in conjunctival swabs from the source bird than in the human samples. One clinic attendant was infected despite using personal protective equipment when handling the bird. This is the first report of PCR analyses of blood and urine samples being used to diagnose human psittacosis, and the first time that the organism load in humans has been compared to that of the infecting bird.