We analyzed data of 76 consecutive patients with myelodysplastic syndrome (MDS) and isolated del(5q) (n=66) or del(5q) plus one additional chromosomal abnormality (n=10) included in our MDS database over the last 26 years. The median age of our patient population was 66.8 years. The male to female ratio was 1:1.7. In all, 14 patients (18%) had advanced MDS with an increased medullary blast count. A total of 17 patients (22%) had significant dysplasia in the nonmegakaryocytic cell lines. Nearly half of the study population showed erythroid hypoplasia in the bone marrow. The projected median survival of patients with isolated del(5q) is 146 months for a median follow-up of 67 months. Patients with an increased medullary blast count and those with an additional chromosomal abnormality have a significantly shorter overall survival (24 and 45 months, respectively) than patients with isolated del(5q). We did not find survival differences for different cytogenetic breakpoints, nor did the amount of dysplasia have an impact on survival in our population. In total, 29 patients have died. Deaths occurred primarily due to transformation into acute leukemia, infection, or cardiac failure. Our data support the current definition of a separate entity of MDS with del(5q) that has been suggested by the World Health Organization.