This study involved descriptive research i epidemiology and aimed at analyzing incidence of pulmonary tuberculosis in suspected out-patients. The certain factors are related to medical care of suspects, prevention, environment, attitude of patients, level of knowledge and self-treatment as well as under-dosage of curative medicine during the first 2 months. The suspected population, who come for treatment at out patient section of central chest hospital, Nonthaburi during July 23, 1987 to January 27, 1988 or a period of 6 months, are selected from those above 15 years of age and have had either coughing symptoms of over 2 weeks, blood splitting sputum or hemoptysis. Questionnaires, chest x-rays, microscopic examination of sputum, culture and insemination, tuberculin test and final medical diagnosis are collected from 623 random samples. The study provided evidence that the incidence of patients 69.3% per 100 persons per 6 months. People during 6 months is the average age of 15-24 years (82.2%) and there are more male than female. Vocational level is 81.0%. unmarried status is 80.4% and 93.8% of students whereas their income level is medium. Treatment factor shows that the suspects are infected by referal system for 5% and 95% of them decide on their own to receive treatment. Average point comparison of patient and non-patient finds that the former are more educated than the lated and the education of significance statistical level is P < 0.0001 Beside, finding result concerning under-dosage during the first 2 months turns out all of those patients, 76.6% receives regular treatment, 11.1% stops receiving treatment and 2.5% stops due to allergy. The passive case detection of specific disease hospital finds that it is helpful in controling tuberculosis since the statistics in term of epidemiology keep changing, in relation to infection, mortality rate as well as other important factors. This study helps us in understanding data which can be used as a guideline to control tuberculous epiemdics in the community.