Introduction: In patients with essential thrombocythemia (ET), the vascular complications contribute to morbidity and mortality. To better predict the occurrence of thrombotic events, an International Prognostic Score for Thrombosis in Essential Thrombocythemia (IPSET-thrombosis) has recently been proposed. We present the application of this score and compare its results with the usual classification system. Method: We retrospectively evaluated the characteristics and risk factors for thrombosis of 46 patients with a diagnosis of ET seen in the last 6 years at Faculdade de Medicina do ABC (FMABC). Results: Thrombosis in the arterial territory was more prevalent than in venous sites. We observed that cardiovascular risk factors (hypertension, hypercholesterolemia, diabetes mellitus, and smoking) were also risk factors for thrombosis (p<0.001). Age over 60 years and presence of JAK2 V617F mutation were not associated with the occurrence of thrombotic events. No patient classified by IPSET-thrombosis as low risk had a thrombotic event. Furthermore, using the IPSET-thrombosis scale, we identified two patients who had thrombotic events during follow-up and were otherwise classified in the low-risk group of the traditional classification. Leukocytosis at diagnosis was significantly associated with arterial thrombosis (p=0.02), while splenomegaly was associated with venous thrombotic events (p=0.01). Conclusion: Cardiovascular risk factors and leukocytosis were directly associated with arterial thrombosis. IPSET-thrombosis appears to be better than the traditional classification at identifying lower risk patients who do not need specific therapy.