DIPSS-plus (the Dynamic International Prognostic Scoring System-plus) includes 8 risk factors for survival in primary myelofibrosis. In the present study of 884 karyotypically annotated patients with primary myelofibrosis, we sought to identify 1 or 2 parameters that can reliably predict death in the first 2 years of disease. After a median of 8.2 years from time of referral to the Mayo Clinic, 564 deaths (64% of patients in the study) had been recorded. Risk factors associated with > 80% 2-year mortality included monosomal karyotype, inv(3)/i(17q) abnormalities, or any 2 of the following: circulating blasts > 9%, leukocytes ≥ 40 × 10(9)/L, or other unfavorable karyotype. Patients with any 1 of these risk profiles (n = 52) displayed significantly shorter overall survival than those otherwise belonging to a high-risk category per DIPSS-plus (n = 298); respective median survivals were 9 and 23 months (hazard ratio 2.2, 95% confidence interval 1.6-3.1; P < .01). The present information complements DIPSS-plus in the selection of primary myelofibrosis patients for high-risk treatment approaches.