A 48-year-old man diagnosed as pulmonary alveolar proteinosis (PAP) received a whole-lung lavage by the conventional lavage technique, but he failed to show any clinical or functional improvement. Therefore, we applied a modified lavage technique of Bingisser resulting in the impressive clinical and functional improvement. We measured the levels of KL-6 in bronchoalveolar lavage fluid (BALF) at selected time intervals. KL-6 levels in BALF were higher during the lavage by the modified lavage technique of Bingisser than the conventional lavage technique. We were able to verify the usefulness of the modified lavage technique of Bingisser by monitoring the levels of KL-6 in BALF. The modified lavage technique of Bingisser may be useful for PAP treatment.