Objectives : This study was performed to report adverse events in Ojeok-san extract powders RCT. Methods : 180 patients with LBP were randomized into groups for a double blind, placebo-controlled clinical study. They received Ojeok-san simple Extract, Ojeok-san complex Extract or placebo in powders, orally dissolved 3times a day for 4weeks. During 4weeks, we researched the symptoms and duration of adverse events and Digest ability, Milk hypersensitivity, Starch hypersensitivity, Caramel hypersensitivity, West-med hypersensitivity, Herb-med hypersensitivity in patients who had adverse events. Results : 52patients(28.9%) had adverse events and of them 44patients(28.9%) had lost adverse events naturally. But 5patients(2.8%) were withdrawn from the research because of the adverse events. Most of the symptoms of adverse event was Gastrointestinal symptom(88.3%) and adverse events frequency was not different from Ojeok-san simple Extract, Ojeok-san complex Extract and placebo. Conclusions : Ojeok-san extract powders had adverse events no different from the placebo, which shows that it is a safe drug.