OBJECTIVES: Hypersensitivity reactions have been reported in Oxaliplatin for the treatment of advanced colorectal cancer (mCRC). The reported incidence of hypersensitivity reactions (HSRs) is approximately 12%, with 1 - 2% of patients developing grade 3 or 4 in severity which may postpone length of stay and incurred extra cost for the treatment of hypersensitivity reactions METHODS: This is a retrospective observational study. Medical records of hospitalized patients with mCRC, who treated with FOLFOX regimen and occurred mild to severe HSRs were identified and reviewed by oncology pharmacist from January 2004 to February 2010. Direct medical cost for the treatment of HSRs and the extra days of hospitalization were calculated. We compared the difference of direct medical cost for patients whose oxaliplatin was discontinued (group A) and those oxaliplatin was continued (group B) for treating mCRC after the computer detected patients’ allergy and the signal was appeared on the screen of physician-order-entry- system. Student t test was used for data analysis. RESULTS: A total of 442 patients with the diagnosis of mCRC and had reported moderate to severe HSRs during the treatment of FOLFOX regimen through our computerized decision supporting system( patients allergy history alert system) were included in this study. Twenty-four of 442 patients reported mild to severe hypersensitivity reactions caused by oxaliplatin. The total direct medical costs for 24 patients were NT$864,352 dollars. The direct medical cost to manage HRSs in group A was higher than that in group B. CONCLUSIONS: Oxaliplatin induced severe hypersensitivity reaction is scare, but it may cause an extra direct medical costs if it is appearance. To develop a computerized alert signal is helpful and is likely to save costs.