Objective. To determine the frequency of sonographically evident upper extremity venous thrombosis in symptomatic cancer patients with and without central venous catheters. Methods. Retrospective review of 573 consecutive upper extremity venous sonographic reports from a 26-month period was performed. Findings including distribution of venous thrombosis, the presence of a central line, cancer type, and miscellaneous findings were recorded. Results. Overall, 514 studies (90%) had satisfactory visualization of all upper extremity vessels; 53 (9%) had limited visualization of 1 or more vessels; and 6 (1%) were inconclusive. Venous thrombosis was present in 227 (40%) of 573 studies. Of the studies with positive findings, there were 186 acute, 13 chronic, 19 fibrin sheath versus nonocclusive, and 9 superficial thromboses. Central venous catheters were present in 325 (57%) of 573 studies. Sonographically evident thrombosis was present in 157 (48%) of 325 studies with central catheters versus 70 (28%) of 248 studies without central venous catheters (P = .001) Conclusions. Upper extremity venous thrombosis is common (40%) in symptomatic cancer patients and is nearly twice as frequent in cancer patients with indwelling central venous catheters.