Background: Oxaliplatin has become one of the major cytotoxic agents for the treatment of gastrointestinal tumors. As a result, several cases of the so-called oxaliplatin-associated hypersensitivity reaction have been documented. Patients and Methods: We have retrospectively evaluated and characterized these reactions in our patient group by reviewing the files of 1,224 patients exposed to an oxaliplatin-containing regimen in order to provide useful clinical information for diagnosis and management. Results: Three hundred and eight (308) patients who have never been exposed to platinum compounds developed symptoms compatible with a reaction to oxaliplatin that was verified by manifestation of at least similar symptoms on rechallenging. The reactions occurred after the first 5 courses, with a median course number of 9 (range 1–24). These reactions could be distinguished as (1) mild reactions occurring in 195 (63%) patients manifesting with itching and small area erythema either during treatment or within the next hours, and (2) severe reactions occurring in 113 (37%) patients within minutes of drug infusion manifesting with diffuse erythroderma, facial swelling, chest tightness, bronchospasm and changes in blood pressure. Oxaliplatin withdrawal was not required in patients with a mild reaction. Forty-eight (42%) patients having a severe reaction with appropriate premedication and prolongation of the infusion duration could tolerate 2–4 subsequent courses. For the remaining 65 (58%) patients, oxaliplatin withdrawal was inevitable because of the very severe reactions occurring on rechallenging. In addition, 3 patients presented with thrombocytopenia and 3 others with hemolytic anemia, all reversible upon oxaliplatin discontinuation. Conclusions: Hypersensitivity reactions to oxaliplatin are underestimated. Although the reactions are not frequent during first courses, in extensively pretreated patients, they may become a serious problem. In the majority of patients, drug discontinuation might not be necessary. In patients manifesting a severe reaction, re-exposure to oxaliplatin should be considered only if the patient can tolerate the reaction and there has been clinical benefit from this therapy. Physicians and nursing staff should be aware of the risk and be well prepared.