Multiple chemical sensitivity (MCS), a syndrome in which multiple symptoms occur with low-level chemical exposure, has not been clarified in detail. The aim of our study was to clarify the clinical characteristics of physician-diagnosed MCS patients in Japan. We analyzed patient characteristics based on the medical records of 106 patients diagnosed with MCS according to the 1999 Consensus and the Japanese diagnostic criteria for MCS. We evaluated subjective symptoms using the Quick Environment Exposure Sensitivity Inventory (QEESI) and compared the QEESI scores with those of four MCS patient groups in the US reported by Miller and Prihoda [Miller, C.S., Prihoda, T.J., 1999b. A controlled comparison of symptoms and chemical intolerances reported by Gulf War veterans, implant recipients, and persons with multiple chemical sensitivity. Toxicol Ind Health 15, 386-397]. Female patients accounted for 74.0%. Most male patients were in their 30s, whereas female ages ranged widely from 10 to 65 years. Among estimated onset factors, those seen in males tended to be workplace related, while female patients showed a variety of factors. Co-morbid allergic disease was present in 84.0% of patients. A significant difference in the QEESI score between male and female patients was found in only one item out of 10 in symptom severity and life impact. However, all 10 items in chemical intolerance were significantly higher in females than in males. The mean QEESI score in the patient group in our study was lower than those in any of the four self-reported patient groups in the US.