The usefulness of the cytology of postbronchoscopically collected sputum (PBS) samples in the diagnosis of neoplastic lung disease has been studied in 113 cases. The overall diagnostic yield of fiberoptic bronchoscopy (FB) alone was 77%, 87% in 77 central tumors and 58% in 36 peripheral ones. With the addition of PBS, the positive results increased to 91% in the 113 cases (p < 0.01), to 94% in central tumors (p > 0.05) and to 83% in peripheral lesions (p < 0.02). In 15 cases PBS offered the unique positive results. 73 cases with histological confirmation showed a good cytohistological correlation in 82%. Our report suggests that PBS is a useful technique in the diagnosis of lung cancer. Its systematic use does not seem to be justified in central tumors, but it is of great value in peripheral tumors when fluoroscopic control is not available.