Purpose: : Skin-sparing mastectomy with immediate reconstruction provides psychological satisfaction and a good cosmetic effect for patients with breast cancer. However, this procedure takes longer operation time than mastectomy, and the risk of pulmonary thromboembolism (PTE) and deep vein thrombosis may be increased. The purpose of this study was to evaluate the incidence of PTE. Methods: Between January and May in 2005, 54 breast cancer patients who underwent skin-sparing mastectomy with immediate transverse rectus abdominalis myocutaneous flap (TRAM) at Asan Medical Center were prospectively investigated according to the clinicopathologic data. Patients were placed in compression stockings on the day of operation, and lung perfusion, inhalation scans,and serum D-dimer assays were performed on the first three postoperative days. If findings were suspicious, we performed embolism computed tomography. We compared patient age, body mass index (BMI), clinical risk factors, operative findings, pathologic results, and the clinical course between PTE patients and non-PTE patients. Results: There were 9 cases of intermediate probability and 6 cases of high probability for PTE according to lung perfusion and inhalation scans, and they underwent embolism CT. Eleven patients (20.4%) were diagnosed with embolism CT or with lung perfusion and inhalation scans;2 patients were symptomatic and 9 patients were asymptomatic.There was significant difference between PTE and non-PTE patients for age, but none for BMI, clinical risk factors, operation time, serum D-dimer, or stage. Conclusion: The incidence of PTE after mastectomy with immediate TRAM is relatively high, and a strategy for the prevention and treatment of PTE is required. Although age is a risk factor for PTE on this study, future studies are needed to determine the risk factors for and to confirm proper treatment and prevention of PTE.