We developed a new type of bronchoscope (BF-2.7T) and cytology brush (BC-0.7T) that permit collection of pulmonary cells during direct observation of the small airways. This kind of cell collection has been previously impossible. With our cytology brush, 3.58 +/- 2.76 x 10(4) cells were collected from small airways. The rate of living cells was 33.13 +/- 3.61 percent from the small airways. Analysis of endoscopic findings and investigation of pulmonary cells are very important for elucidating the pathophysiologic state of the small airways. The use of the BF-2.7T allowed collection of cancer cells under direct endoscopic vision in all five patients with peripheral lung cancer. They also contribute to our understanding of the relationship between exogenous factors and cells that compose the lung, and will provide means for treatment and prevention of diseases.