To analyze the clinical significance of the extent of lymphovascular space invasion (LVI) in patients with uterine serous carcinoma. After IRB approval, 232 patients with uterine serous carcinoma from the pathology databases of 4 large academic institutions were included. Patients were divided into 3 groups based on extent of LVI. Extensive LVI (E-LVI) was defined as ≥3 vessel involvement; low LVI (L-LVI) was defined <3 vessel involvement; and the third group consisted of tumors with no LVI (A-LVI). The association between LVI and myometrial invasion, cervical involvement, lower uterine segment involvement, positive peritoneal washings, lymph node involvement, stage, and survival were analyzed. Of 232 patients, 47 had E-LVI (20.3%), 83 had L-LVI (35.8%), and 102 had A-LVI (44%). A total of 9.8% of the patients with A-LVI had lymph node involvement as compared with 18.1% in the L-LVI group and 55.4% in the E-LVI group (P<0.0001). Fifty-nine percent of the patients in A-LVI, 85% in L-LVI, and 100% in the E-LVI group demonstrated myometrial invasion (P<0.0001). Cervical involvement was noted in 23%, 43%, 66% (P<0.0001) and lower uterine segment involvement involvement in 31%, 43%, and 42% of A-LVI, L-LVI, and E-LVI (P<0.0001), respectively. Stage III and IV disease were seen in 29%, 38%, and 79% of the patients with A-LVI, L-LVI, and E-LVI, respectively (P<0.0001). The median overall survival was 172, 95, and 39 mo for the A-LVI, L-LVI, and E-LVI groups, respectively (P<0.0001). The racial distribution was significant with African American patients demonstrating significantly more L-LVI (27.8%) and E-LVI (40.4%) when compared with A-LVI (19.6%) (P=0.040). In a subgroup analysis including patients with Stage I and II (n=123) revealed median survivals of 172, 169, and 38 mo in the A-LVI, L-LVI, and E-LVI groups, respectively (P<0.0001). Fifty percent of these patients with E-LVI, 20% in L-LVI group, and 15% in A-LVI group had disease recurrence (P=0.040). The extent of LVI was associated with multiple pathologic factors and was found to be a negative prognostic factor for overall survival and disease recurrence.