Chlamydia psittaci , the name veterinarians commonly call the parrot fever organism, has been one of the most common bacterial diseases that infects pet birds. This intracellular bacterium has been the subject of much research regarding avian species as well as humans and other animal groups. The genesis of this research is not only to improve diagnostic capabilities and animal health, but also because this is a zoonotic disease that has the ability to cause severe clinical disease in infected humans. The advent of antibiotics and diagnostic techniques have lessened the pathogenic impact of Chlamydia psittaci , but has not removed much of the mystery surrounding its diagnosis and treatment in animals, especially avian species. Molecular biology has enabled scientists to unravel some of the mysteries, with many of these findings annually contributing to the scientific knowledge base. Recent scientific studies have led to new findings on classification and diagnostic testing of the C. psittaci organism. A protocol to control C. psittaci infection among humans and pet birds has recently been published by the Centers for Disease Control and Prevention.