The number of psittacines kept as pets is rapidly increasing in Germany. The main cause of disease and death in these and other tropical birds are respiratory tract affections. Yet, a lack of consolidated, systematic research on the anatomy and pathology of these affections in gray parrots and amazons still widely persists. In a first step examinations on the anatomy of the respiratory tract of gray parrots and amazons were performed. By the means of computed tomography, morphological structures as well as volume and density measurements were conducted on this subject for the first time. By this, important, fundamental knowledge on the anatomy of the different parts of the psittacine respiratory tract as well as aspects of volume and density were gained. The computed tomography (CT) proved to be a valuable, informative and due to its non-invasive application, a careful method for examining patients. These aspects recommend it in the examination and research projects of other endangered exotic species as well. Due to its ability to image a longitudinal cross section as a standard cross section--which is not possible in humans or large animals--better information on the expansion of organs/structures in the longitudinal body axis could be obtained. A remarkable reduction of costs and performance time as well as the possibility of a direct comparison with conventional radiographs is also given. In a second step, with the use of the CT, pathological alterations in diseased gray parrots and amazons were then assessed based on anatomical data gained in the previous investigations on healthy birds. These results will be described later in a second part.