Aetiological factors of the myelodysplastic syndromes (MDS) are largely unknown, with the exception of alkylating agents, ionizing radiation and benzene. Some other risk factors have been suggested by the few epidemiological studies reported (solvents, ammonia, exhaust gases, metals, pesticides, alcohol). We performed a case–control study to assess the relationship between occupational or environmental factors and MDS. Two hundred and four patients with newly diagnosed MDS, and 204 sex- and age-matched controls were included. Medical history, demographic data, lifetime exposure and hobbies were obtained. Qualitative and quantitative exposure to chemical and physical hazards were evaluated with the patients and reviewed by a group of experts in occupational exposure. The median age was 70 years and 62% of the patients were men. In univariate analyses, we found relationships between MDS and smoking habits, gardening, occupations such as health professionals, technical and sale representatives, machine operators, agricultural workers, textile workers, qualitative occupational exposures (exposed/non-exposed) to oil, solvents, ammonia, pesticides, fertilizers, cereal dusts, contact with poultry or livestock and infective risk, and lifetime cumulative exposure to solvents, oil, textile dust and infective risk. The main risk factors of MDS determined by multivariate analyses (conditional logistic regression) were, being an agricultural worker [odds ratio (OR) = 3·66; 95% confidence interval (CI) 1·9–7·0], textile operator (OR = 3·66; 95% CI 1·9–7·9), health professional (OR = 10·0; 95% CI 2·1–48·7), commercial and technical sale representative (OR = 4·45; 95% CI 1·4–14·6), machine operator (OR = 2·69; 95% CI 1·2–6·0), living next to an industrial plant (OR = 2·45; 95% CI 1·5–4·1), smoking (OR = 1·74; 95% CI 1·1–2·7) and lifetime cumulative exposure to oil (OR = 1·1; 95% CI 1·0–1·2). Further studies should be performed to assess specific exposures more precisely and it would be of interest to develop a map of haematological malignancies according to industrial background.