Kazuhiro Yamaguchi was born in Osaka, Japan. He graduated from School of Medicine, Keio University, Tokyo, Japan in 1975 and completed his doctor course (Internal Medicine) at the Keio University in 1979. He received the PhD degree from the Keio University in 1981. From 1982 to 1984, he was a Research Fellow at the Max-Plank Institute for Experimental Medicine, Göttingen, Germany. He was a Head at the Pulmonary Division, of Keio University Hospital from 1991 to 2004. From 2004 to 2010, he was a Deputy Director of Sano Kosei General Hospital, Tochigi, Japan. From 2010 to 2015, he was a Professor of Tokyo Women’s Medical University and held the Director position at Comprehensive Medical Center of Sleep Disorders, Tokyo Women’s Medical University. From 2014 to the present, he is a visiting professor of Tokyo Medical University. From 2015, he doubles as the head of Respiratory Medicine at Tohto Clinic, Kenko-Igaku Association, Tokyo, Japan. He was Councilors of Japanese Respiratory Society, Japan Society of Respiratory Endoscopy, Japanese Society of Lung Cancer, Japanese Society of Tuberculosis, Japanese College of Angiology, and Japanese Society of Microcirculation. Since 1996, he is an Editorial Board Member of Respiratory Physiology & Neurobiology (RESPNB). He was an Editorial Board Member of International Scholarly Research Network (ISRN), Pulmonology, PLoS ONE, Annals of the Japanese Respiratory Society, and Journal of the Japan Society of Respiratory Endoscopy. He served as one of the principal members for constructing the Guideline of Diagnosing and Treating COPD and the Guideline of Respiratory Function Tests in Japan.