Although myelodysplastic syndromes (MDS) have been increasingly diagnosed in recent years, precise data on their prevalence and incidence are still lacking. Due to difficulties of diagnosis and classification, large-scale population-based studies that are required for obtaining truly representative data on the epidemiology of MDS are currently not available. Our present knowledge of the incidence and other epidemiological characteristics of MDS is based on a few regional studies performed by authors with a long-lasting interest in these hemopathies. Despite certain limitations, these studies have consistently shown that MDS are relatively common hematological malignancies. Their crude incidence varies from 2.1 to 12.6 cases per 100,000 people per year. Among the age group that is mainly affected, people older than 70 years, we are now faced with incidence rates of about 15 to 50 cases per 100,000 people per year. The recent increase in MDS incidence observed in some studies is probably not the result of an actual increase in the number of cases, but reflects improvements in geriatric medical care and diagnosis.