Cytogenetic classification by the revised international prognostic scoring system (IPSS-R) and the prognostic value of monosomal karyotype (MK) were assessed in 783 patients with primary myelodysplastic syndromes (MDS). At 22 months median follow-up, 562 (72%) deaths were recorded. Percentages of patients with IPSS-R "very good", "good", "intermediate", "poor" and "very poor" cytogenetic categories was 5%, 63%, 18%, 4% and 10%, respectively. The corresponding median survivals were 21, 40, 24, 18 and 6.5 months and the inter-group differences (good vs. very good/intermediate/poor vs. very poor; p<0.01) or similarities (very good vs. intermediate vs. poor; p=0.79) were not significantly modified in multivariable analysis. Results were similar when analysis was restricted to 602 patients managed by supportive care. MK adversely affected survival in both poor and very poor karyotype groups (p<0.01). In conclusion, we were unable to confirm the prognostic superiority of IPSS-R-very good karyotype or prognostically distinguish between very good, intermediate and poor karyotypes. Furthermore, we show additional prognostic information from MK in poor/very poor karyotype.