The SBS is characterised by irritations of mucosa, vegetative complaints such as headache and fatigue as well as mental health impairment, depression and irritability (WHO definition). Since well-being is a subjective perception, the individual self report is mandatory. In the ProKlimA project a modular questionnaire was developed in which SBS symptoms, general aspects of well-being and function as well as psychosocial characteristics were included in a modular fashion. Assessment included sensory irritation (SI list), psychosocial characteristics (POMS) and bodily complaints, assessed with a standard German complaint list (BL). In addition the individual indoor-air perception, stress reactions, the perceived work-environment, health locus of control, life satisfaction and work related use were assessed. Analysis of the questionnaire filled out by 4596 employees at the first measure point showed a high consistency of responses. Psychometric testing showed a high reliability and acceptable validity of the questionnaire. The results suggests that well-being within the SBS complex can be assessed in a methodological way and that the developed questionnaire can be used to assess SBS symptomatology as well as psychosocial determinants also in further SBS studies.