Background: The concomitant prevalence of obstructive sleep apnea hypopnea syndrome (OSAHS) and pulmonary embolism (PE) is strikingly high, and therefore we studied the patients with PE to determine whether those who had OSHAS required greater warfarin doses to achieve a therapeutic international normalized ratio (INR). Methods: By using computer tomographic pulmonary angiography or pulmonary angiography, we identified and recruited 97 patients with PE and all underwent polysomnography. Warfarin was initiated at a dose of 3mg/day and modified to adjust the INR to the range of 2.0-3.0. Results: OSAHS patients (n=32) required a significantly higher dose of warfarin than their non-OSAHS counterparts (5.01mg vs 3.61mg, P<.001). This difference still existed between the two groups after adjusting for covariates (achieved INR value and weight). Logistic analysis suggested that OSAHS was an independent risk factor for high dose warfarin (OR 5.715, P<.001). On admission, OSAHS patients had a lower mean value of INR and prothrombin time but higher plasminogen (PLG) activity compared to non-OSAHS patients. Other coagulation indices were not significantly different between the two groups. Except for the PLG activity (r= .273, P= .026), the correlation between the warfarin dose and the baseline coagulating indices wasn't significant. Conclusions: Our findings indicate that factors associated with OSAHS, such as hypercoagulation, may explain the need for higher doses of warfarin in treating patients with PE. © 2014 Elsevier Inc.