Oxaliplatin (L-OHP) is a new third-generation platinum which is efficacious in treating advanced unresectable recurrent colorectal cancer as a first-line regimen. The marketing authorization was given in Japan in March, 2005. Its increased use has resulted in rare serious adverse effects, including anaphylactic shock. We experienced a case that developed anaphylactic shock by L-OHP. We report a 69-year-old man who was treated for recurrent colorectal cancer who underwent systemic chemotherapy with FOLFOX 4. After eight cycles he developed severe L-OHP associated neuropathy and lung metastases was a progressive tendency. The FOLFOX 4 regimen was discontinued and another modality, FOLFIRI regimen, was used. After eight cycles of FOLFIRI regimen, lung and liver metastases showed progressive disease for response assessment by RECIST criteria. Although a patient was stopped L-OHP for neurotoxicity, neuropathy was disappeared after 4 months interval. Therefore, we reintroduced L-OHP, FOLFOX 4 regimen. Anaphylactic shock occurred in the second cycle of reintroduction of the FOLFOX 4 regimen (total 10 cycles), 30 minutes after infusion of L-OHP. L-OHP infusion was immediately withdrawn and he was treated with intravenous hydroxyzine hydrochloride and methylprednisolone. The anaphylaxis symptoms resolved in 30 minutes. Chemotherapy based on L-OHP for unresectable recurrence colorectal cancer causes anaphylactic shock as a rare severe complication. The prediction factor is not proved. We should take steps for early detection of anaphylactic reaction and perform the appropriate treatment.