['To locate small deep pulmonary nodules under thoracoscopy, we developed a long-lasting point marker termed "colored collagen."', 'Colored collagen is composed of 0.8% atelocollagen, 5% methylene blue, and 32% contrast medium. The affinity between atelocollagen and methylene blue was examined in a washing test using 2 mol/L of NaCl. For clinical application, a computed tomography-guided colored collagen injection was performed in 11 patients to localize 11 deep pulmonary nodules, which were less than 20 mm in diameter.', 'The washing test showed that atelocollagen and methylene blue combined with each other firmly. An experimental study using rabbit lung showed that the colored collagen stayed at the injected site for 10 days without toxicity. In clinical application, the colored collagen could be seen as a clear spot using the thoracoscopy 1 to 4 days after the injection in all of the 11 pulmonary nodules. There was no complication except for a slight pneumothorax in 2 patients.'] Is colored collagen a long-lasting point marker for small pulmonary nodules in thoracoscopic operations?