Panitumumab was approved in June 2010 for use in the treatment of unresectable advanced/recurrent colorectal cancer. Here, we report outcomes and adverse events of panitumumab combination therapy or single-agent chemotherapy for K-ras wild-type unresectable or recurrent colorectal cancers. Our study focused on first-line treatments. The study involved 18 patients who started receiving panitumumab in October 2010. Nine patients received panitumumab as a first-line treatment; 4, as a second-line treatment; and 5, as a third-line or subsequent treatment. The overall response rate was 27.8%. Among the patients who received panitumumab as a first-line treatment, the response rate was 55.6%. Grade 1 and 2 skin disorders were common adverse events. Grade 2 interstitial pneumonia was observed in 1 patient(5.6%). Grade 3 or higher events comprised peripheral neuropathy in 1 patient(5.6%)and neutropenia in another patient(5.6%). The treatment was beneficial, and metastatic foci were resected in 3 patients. In this study, the only adverse events of Grade 3 or higher were 1 case each of peripheral neuropathy and neutropenia. Accordingly, adequate control seemed possible. The specific line of treatment that panitumumab should belong to remains controversial. However, active initiation as first-line treatment should be considered for cases in which resection of metastatic foci can be expected from tumor reductions due to panitumumab.