OBJECTIVES: To estimate the ICU drug cost impact of clinical pharmacists’ interventions at the Ghent University Hospital.   METHODS: A patient cohort with pharmacist intervention (I) was compared with a control group (M) (Jan 08 – Dec 11). Matching criteria were admission year, hospital length of stay (LOS), All Patient Refined Diagnosis Related Group (APR-DRG), Major Diagnostic Category (MDC), mortality rate, age. Generic drug names, selected from a pharmacists’ ICU - intervention database were included in the analysis if the cost/daily defined dose (WHO.int) multiplied with the intervention rate was > 50€: acetaminophen, acyclovir, ceftazidim, enoxaparin, erythromycin, (es)omeprazole, fluconazole, levofloxacin, linezolid, meropenem, piperacillin tazobactam, ranitidin, somatostatin, teicoplanin, vancomycin, (val)ganciclovir, voriconazole. The average ICU drug cost was compared between groups and a “drug cost per number of used units” ratio was calculated: lower ratio for (I) was considered as a more efficient use. (Data are in % or median with interquartile range IQR; statistical analysis in SPSS, Chi Square Test; p=0.05).                RESULTS: Eighty-nine ICU patients receiving intervention were matched with 167 patients. Median LOS was respectively 39 (22 – 72) days for (I) and 35 (20 – 71) (M). Mortality rate was 29% (both groups). Most prevalent APR-DRG was septicemia: 16.9% (I); 18.6% (M). Average ICU drug cost was 346.75€ (I) compared to 397.64€ (M) (p<0.001); for the selected drugs 168.23€ (I) and 144.52€ (M) (not significant). Ratios in favour of (I) were found for ceftazidime (p<0.001), meropenem (p<0.001), piperacillin tazobactam (p<0.001) and teicoplanin (p=0.001).       CONCLUSIONS: Average ICU drug cost was lower in a group of patients receiving pharmacist interventions but this trend could not be attributed to the 19 most costly and prevalent drugs in intervention. However, for 4 of these drugs data suggest a more efficient use. This finding needs to be confirmed with prospective data and to be balanced with health outcomes.