Aim. To investigate clinical manifestations and diagnostic difficulties in patients with HIV/AIDS in the practice of therapeutic units of a multidisciplinary hospital. Subjects and methods. The investigation included 65 HIV/AIDS patients admitted to the therapy units of a Saratov Regional clinical hospital in 2007 to 2011. The clinical features of HIV/AIDS, immunological status, and viral load were studied. Results. The structure of the clinical manifestation of HIV/AIDS showed a preponderance of lung injury in 45 (69%) patients. There were hematological disorders in 38 (58%) patients and nephropathy in 33 (51%); 11 (17%) patients were diagnosed with infective endocarditis. Rheumatic symptoms and syndromes mimicking HIV/AIDS were found in 10 (15.4%) patients. The degree of immune disorders was most severe in patients with pulmonary dissemination and rheumatic masks and mutually related to the rate of cutaneous manifestations. The specific features of lung injury, infective endocarditis, pulmonary hypertension, rheumatic symptoms, and kidney injury were discussed in HIV/AIDS patients having different causes for admission to specialized therapy units. Conclusion. In connection with the clinical polymorphism of HIV/AIDS, physicians of all specialties should be alert for the possible clinical manifestations of this disease to timely examine patients.