Obinutuzumab frequently triggers an infusion reaction(IR). In the GALLIUM study, despite the use of corticosteroids, antipyretic analgesics, and antihistamines to prevent IR, IR occurred at a high frequency of 68.2% for all Grades and 12.4% for Grades 3 or higher. The dose of methylprednisolone was increased from 80 mg administered in the GALLIUM study to 125 mg, and the development of IR was investigated in 30 patients with follicular lymphoma who received the initial dose of obinutuzumab. The incidence of IR was 43.3% for all Grades and 0% for Grades 3 or higher, and no serious IR was observed. It also had no effect on infectious diseases. Increased doses of corticosteroids were well tolerated and suggested as an effective method for reducing the frequency of IR.