Vancomycine serum levels were measured in 198 cancer patients with documented grampositive bacteremia and twenty two failed. Failures were analyzed for risk factors of therapy failure. Only 8 of 22 showed low serum peak or through vancomycin levels. One patient was treated less than 7 days, 9 had persisting and 4 catheter associated bacteremia. Bacteremias due to VAN resistant strains were excluded. In 14 out of 22 patients, multiple or one risk factor could be determined, but in 8 patients, no risk factor was found. Hence the, case control study was conducted to compare the group of failures in 22 patients with a group of patients with underlying disease and neutropenia treated successfully within the same period and same antibiotic policy at the same cancer center, by VAN for gram-positive bacteremia. Persisting, catheter associated and enterococcal bacteremias were the only statistical significant risk factors predicting a therapy failure in cancer patients. Neither Vancomycine serum peak nor through levels predicted the outcome: failure or cure of gram-positive bacteremia in cancer patients. (Tab. 1, Ref. 5.).