The photofluorography is the single best method for mass survey for defection of chest diseases, especiallyfor determination of the pulmonary tuberculosis. However, the reliability of photofluorography as a diagnosticmethod is mostly depend upon quality of films, reader's perceptual experiences and his knowledge on chestdiseases, and upon the process of interpretation, i.e., interpretation by single or dual reading. A statisticalanalysis and discussion were made on the results of 1.394,581 photofluorograms in the mass survey which hadcarried out from 1969 to 1971, Results were as follows: 1. The ratio of positive cases to all examinees shows arange of 1.45%-4.05% 2. The most frequent disease in the positive cases was minimal pulmonary tuberculosis. 3.There it showed good expectancy for detecting positive cases at the second reading which was interpreted byexperienced radiologists than at the first reading done by the other doctors. It gives an accent one an importanceof dual reading by the experienced radiologists for the higher reliability in diagnosis of chest disease.