BACKGROUND: Abnormalities involving chromosome 7 are frequent in myelodysplastic syndrome (MDS) and suggest a poor prognosis. METHODS: The authors examined the hypothesis that the clinical features and survival associated with isolated deletion (del) of part of the long arm of chromosome 7 (7q) in MDS are different from those associated with isolated monosomy 7 (complete loss of chromosome 7). In total, 133 patients with a diagnosis of de novo MDS (according to the World Health Organization WHO classification) and chromosome 7 abnormalities in the Spanish MDS Registry were evaluated retrospectively. Four karyotypic groups were identified: isolated del(7q) (n = 29), isolated monosomy 7 (n = 27), del(7q) with additional abnormalities (n = 24), and monosomy 7 with additional abnormalities (n = 53). RESULTS: Isolated del(7q) was more frequent in patients with less advanced MDS according to the WHO classification or the International Prognostic Scoring System. In addition, isolated del(7q) was associated with fewer blasts in bone marrow than other cytogenetics groups. Survival was significantly superior in patients with isolated del(7) than in those with isolated monosomy 7, del(7q) with additional abnormalities, or monosomy 7 with additional abnormalities. On multivariate analysis, age, the percentage of blasts in bone marrow, and other chromosome 7 abnormalities apart from isolated del(7q) were identified as independent risk factors for survival. CONCLUSIONS: The current results demonstrated that patients who had MDS with isolated del(7q) had some distinct clinical‐pathologic characteristics as well as better survival than patients who had MDS with isolated monosomy 7. Cancer 2012;. © 2011 American Cancer Society. Abnormalities involving chromosome 7 are frequent in myelodysplastic syndrome (MDS) and suggest a poor prognosis. In this study, the authors observed that isolated patients who had MDS with deletion of part of the long arm of chromosome (7q) had distinct clinicopathologic characteristics and better survival than patients who had MDS with isolated monosomy 7 (complete loss of chromosome 7). Therefore, the current results indicate that isolated 7q deletion no longer should be considered in the same prognostic category as monosomy 7.