In this multicenter study on multiple chemical sensitivity (MCS) 291 environmental medicine (EM) patients were examined in 6 (year 2000) and later 5 (1st half of 2003) environmental medicine outpatients centres, located in Aachen, Berlin, Bredstedt, (Freiburg), Giessen and Munich. The EM patients were 89 men (30.6%) and 202 women (69.4%) with ages between 22 and 80 (on average 48 years). The sample is representative especially for university-based environmental outpatient departments and represents a cross-sectional study-design with an integrated case-control study (MCS vs. Non-MCS). The data was acquired by means of an environmental medicine questionnaire, a psychosocial health questionnaire and a medical base line documentation. The hypothesis guided evaluation of the project showed that the patients' heterogenic health complaints neither indicate a characteristic set of symptoms for MCS, nor do they prove a systematic connection between complaints and the triggers implicated. Furthermore no evidence could be found for a genetic predisposition, or obvious disturbances of the olfactory system. The standardised psychiatric diagnostics applying the CIDI demonstrated that the EM patients in general and particulary the MCS-subgroup suffer significantly more often from mental disorders than the age- and sex-matched general population and that for most of the patients these disorders began well in advance of the environment-related health complaints.