Data on myelodysplastic syndromes (MDS) are seldom collected by cancer registries and unbiased findings from population-based studies remain rare. We report detailed information on MDS in a well-defined French population in the period 1980-1990. The crude incidence rate was 3.2 per 100000 per year and no significant change in incidence was noted in the study period. The sex ratio was 1.9 and the male predominance was present in all age groups. We observed a rise in incidence after 60 years of age but no significant change in incidence of MDS as a whole was observed over the period studied. Refractory anaemia with excess of blasts (RAEB) was the most frequent subtype. Overall 5 year transformation rate of MDS was 31% (+/- 4%) but it was 100% in RAEB in transformation. The observed 5 year survival rate was 23% +/- 3% and the corresponding corrected rate was 33%. The prognosis of RAEB in transformation was worse than the prognosis of other subtypes (P < 0.01). Discrepancies with epidemiological data from other European countries are discussed.