BACKGROUND This study was designed to determine the accuracy of bronchoalveolar lavage fluid cytology (BAL) using histopathologic examination of transbronchial biopsy specimens as the gold standard in diagnosis of lung carcinoma at our center. METHODS A retrospective study was conducted to investigate a total of 388 patients who were suspected of having lung cancer and had undergone fiberoptic bronchoscopy in Shahid Sadoughi hospital from 2006 to 2011. Lung masses were proven to be malignant by histology. RESULTS Transbronchial lung biopsy (TBLB) identified malignancy in 183 of the 388 cases, including 48 cases (26.2%) with adenocarcinoma, 4(2.1%) with bronchioloalveolar carcinoma, 47(25.6%)with squamous cell carcinoma, 34(18.5%) with well-diffentiated neuroendocrine carcinoma, 35(19.1%) with small cell carcinoma, 14 (7.6%) with non-small cell carcinoma, and 1 (0.54%) with large cell carcinoma. A total of 205 cases were correctly classified as negative. BAL was also performed in 388 patients; 86/103 cases were consistent with the final diagnosis of lung cancer and 188/285 cases were correctly classified as negative. The sensitivity of BAL was 46.9%(CI:41.9%, 51.8%)) and its specificity was 91.6%(CI:88.8%, 94.3%). BAL had a positive predictive value (PPV) of 83.4%(CI:79.7%, 87.1%) and a negative predictive value (NPV) of 65.8%(CI:61%, 70.5%). The overall accuracy of BAL was 70.5% and the exact concordance was 39%. CONCLUSIONS Our findings suggest that BAL cytology is not sensitive but is a specific test for diagnosis of lung carcinoma. If transbronchial lung biopsy is combined with bronchoalveolar lavage, the positive diagnostic rate will be further elevated.