The material is based on the autopsy findings collected over 15 years (1975-1989). Findings related to 748 fatal outcomes were subjected to analysis in which 90 (12%) cases were misdiagnosed regarding the principal disease. A percentage of diagnostic errors with respect to tuberculosis was 1.8 on the whole and in the diagnosis of clinical forms and phases it was considerably higher-15.9 and 19.4, respectively. Hyperdiagnosis was typical of disseminated tuberculosis and caseous pneumonia, while hypodiagnosis--of primary, fibrocavernous tuberculosis and post-tuberculous changes. A percentage of hypodiagnosis in nontuberculous pathology varied from 12.5 to 50. Dynamic observation by the five-year plans demonstrated an increase in the percentage of misdiagnosis of the concurrent pathology and its decrease when the phase of a specific process was established. Purely medical errors accounted for 75% of misdiagnosis.