To identify problems in early diagnosis of tuberculosis and to design countermeasures against the disease, we examined the status of active tuberculosis among patients admitted to a university hospital that did not have an isolation ward for tuberculosis. Between 2005 and 2007, we analyzed demographic characteristics, disease type, chest radiologic findings, and the process leading to diagnosis. Active tuberculosis was diagnosed after admission in 55 patients (34 males and 21 females): pulmonary tuberculosis, 26; tuberculous pleuritis, 13; tuberculous meningitis, 6; miliary tuberculosis, 4; tuberculous pericarditis, 3; lymph-node tuberculosis, 2; and tracheal and bronchial tuberculosis, 1. Although radiographic examinations provided abundant information, chest radiography showed normal findings in 7 patients (12.7%). Computed tomographic scanning was useful for detailed evaluation of abnormalities. Twenty patients (36.4%) were given diagnoses at departments other than ours (Department of Pulmonary Medicine). Numbers of days between hospital admission and diagnosis of tuberculosis (50th percentile/80th percentile) were 8.0/37.8 for miliary tuberculosis, 8.0/8.0 for tracheal and bronchial tuberculosis, 7.5/17.8 for tuberculous pleuritis, 7.0/8.8 for tuberculous pericarditis, 6.0/15.6 for pulmonary tuberculosis, 3.5/4.4 for lymph-node tuberculosis, and 1/1 for tuberculous meningitis. Early diagnosis of tuberculosis requires adherence to the following precautions. Tuberculosis should be suspected in any patient with respiratory symptoms. Sputum tests for acid-fast bacteria should be performed at least three times initially. If findings on chest X-ray films are equivocal, high-resolution computed tomography should be performed to confirm details of shadows and to detect minimal pulmonary shadows or cavitary lesions. Physicians from all specialties should be repeatedly informed about the risk of tuberculosis and should include tuberculosis in the differential diagnosis in patients suspected to have pulmonary diseases.