We conducted a retrospective record review to determine the frequency of venous thromboembolism (VTE) in patients with diffuse large B-cell lymphoma (DLBCL). All records from 1990 to 2001 of patients with the diagnosis of DLBCL at a tertiary care hospital were reviewed. Those with transformation from low-grade lymphoma, central nervous system lymphoma, HIV-related lymphoma or with incomplete records were excluded. All episodes of symptomatic VTE confirmed by imaging studies that were either present at diagnosis or occurred during initial treatment were identified. VTE occurred in 27 of 211 patients (12.8%). Stage I disease was associated with a low risk, whereas a high international prognostic index score increased risk. Of patients with VTE, thrombosis was present at diagnosis in 37% and occurred during the first chemotherapy cycle in 22% and during the first three cycles in 82%. The median survival of patients with VTE was 1.04 years [95% confidence interval (CI) = 0.75 - 1.33] compared to 5.2 years (95% CI 1.8 - 8.6) for those without VTE (P = 0.038). We conclude that VTE is a frequent complication of DLBCL that occurs particularly at diagnosis and during initial therapy, and it is associated with a worse prognosis.