Aims: To evaluate the association between psychosocial workplace factors and dementia in a case-control study. Methods: Patients with dementia (aged 55-99 years) were recruited from 23 general practices in the city of Frankfurt-on-Main and surrounding area in 1998-2000. Of these, 108 were suffering from possible Alzheimer's disease, 59 from possible vascular dementia, and 28 from secondary or unclassified dementia. A total of 229 control subjects (aged 60-94 years) was recruited from the same study region: 122 population controls and 107 dementia-free ambulatory patients. A detailed job history was elicited in a structured personal interview (next-of-kin interviews of cases). Psychosocial work exposure was assigned to cases and control subjects by linking lifetime job histories with a Finnish job-exposure matrix. Data were analysed using logistic regression, to control for age, region, sex, dementia in parents, education, smoking, and the psychosocial network at age 30. Results: There were decreased odds ratios for high challenge at work, high control possibilities at work, and high social demands at work. High risks for error at work revealed a significant positive association with the diagnosis of dementia. Restriction of the analysis to cases with possible Alzheimer's disease or to cases with possible vascular dementia led to similar results. Conclusions: These results support a role for psychosocial work factors in the aetiology of dementia. As an alternative explanation, people might have chosen jobs with poor work factors due to preclinical dementia, which becomes clinically manifest decades later.