The long-term outcomes of pulmonary thromboembolism (PTE) and/or incidence of chronic thromboembolic pulmonary hypertension (CTEPH) are not well documented. Three hundred twenty-five consecutive cases objectively diagnosed with PTE monitored for an average 16.3 months (6-50.7 months) were investigated. Data concerning recurrence, residual thrombus, mortality, and CTEPH in particular were collected. Chronic thromboembolic pulmonary hypertension frequency acute first episode of PTE was 4.6%. Chronic thromboembolic pulmonary hypertension developed within 12 months after PTE attack in approximately 80% of patients and it did not occur after 2 years. Residual chronic thrombus was determined at the 3rd month in 48% of cases post-PTE, at the 6th month in 27.4%, and at the 12th month in 18.2%. At multivariate regression analysis, systolic pulmonary arterial pressure > 50 mm Hg, hazard ratio: 10.1 (95% confidence interval: 4.1-71.2) were predictors of CTEPH. Chronic thromboembolic pulmonary hypertension develops as a serious complication in a significant number of cases with PTE. Closer monitoring of high-risk cases in particular is important in terms of early diagnosis and treatment.