This study was aimed to investigate the correlation of thrombosis with increased platelet turnover in essential thrombocythemia. According to presence or absence of thrombosis, 26 patients with ET were divided into two groups. Reticulated platelets (RP) were measured by flow cytometry and 26 healthy volunteers were selected as healthy controls. The ET patients with thrombosis were treated with hydroxyurea and interferon-alpha. The results demonstrated that the ET patients with thrombotic events had a significantly higher RP percentage (14.8% +/- 7.2%) than that in both asymptomatic ET patients (4.5% +/- 2.3%) and normal control (3.3% +/- 1.5%), (P < 0.05); the RP percentage in asymptomatic ET patients did not differ significantly from controls. ET patients with thrombosis also had a significantly higher absolute RP (ARP) count than those in ET patients without thrombosis [(176 +/- 37) x 10(9)/L vs (46 +/- 12) x 10(9)/L]. The ET patients with thrombosis were successfully treated with hydroxyurea plus INF-alpha, the RP percentage and ARP counts obviously reduced. In conclusion, when the ET patients had thrombotic events, those patients had a significantly higher RP percentage and ARP compared with patients without thrombosis and healthy controls. The ET patients with thrombosis were successfully treated with hydroxyurea plus INF-alpha.