BACKGROUND AND AIM: The objective of this study was to check if clinical parameters could help us determine the optimal dose of thrombolytic therapy for patients with acute pulmonary thromboembolism (PTE). METHODS: This was a retrospective cohort study. The data were obtained through an examination of medical records and the use of an existing clinical database. A total of 367 individuals admitted to a tertiary care hospital between 2016 and 2019 and diagnosed with PTE were evaluated. The study includes people who had massive or submassive thromboembolism that required thrombolytic therapy. There were two rt-PA dosage groups (100 mg rt-PA and 50 mg rt-PA). RESULTS: A total of 81 patients, 43 females and 38 males, were evaluated. Thirty-one of the patients were administered 100 mg rt-PA and 50 were administered 50 mg rt-PA. The mean age of patients in the 100 mg rt-PA group was 57±18 years, while it was 72±11 years in the 50 mg rt-PA group, with a statistically significant difference of p<0.001. In the malignancy 50 mg rt-PA group, the most frequent risk factors were deep vein thrombosis history 100 mg rt-PA (p=0.54 and p=0.04, respectively). Clinical findings at the time of application were similar in both groups except for systolic blood pressure. Systolic blood pressure was lower in the 50 mg rt-PA group (p=0.03). Especially the change of pulse up to the 60th minute was statistically significant in both 100 mg rt-PA and 50 mg rt-PA groups (p=0.01 and p=0.002, respectively). The change of saturation up to the 60th minute was statistically significant in the 50 mg rt-PA group (p=0.003). CONCLUSIONS: While both 100 mg and 50 mg rt-PA are applied, meaningful activity on clinical parameters is in the first 60 min. In particular, the change in pulse and saturation may be more guiding in the follow-up of treatment effectiveness. The significant improvement of clinical parameters, especially pulse and saturation, in the first hour may suggest that lower dosage rt-PA and lower administration duration may be effective in acute PTE.