Prevention of hospital-acquired venous thromboembolism (VTE) is a strongly recommended patient safety practice. This retrospective review of hospital-acquired VTE at one tertiary care hospital found that many patients who developed VTE while hospitalized were prescribed appropriate prophylaxis but did not receive all of the prescribed doses. The authors point out that since current quality metrics measure only prescription of VTE prophylaxis and not actual administration, they may overestimate hospital performance on this safety issue. Moreover, nearly half of the patients with VTE had received prophylaxis that is currently considered optimal, an important finding since VTE is often referred to as a "preventable adverse event."