Phenolic compounds in fruits and vegetables are powerful antioxidants, which are regularly consumed by humans.During the past few decades, the role of phenolics as natural antioxidants and free radical scavengers against cardiovascular diseases and cancer has attracted considerable public and scientific interest.Many separation and analytical techniques have been developed to characterize and quantitate phenolic compounds in fruits, vegetables and other natural plant products.As yet, progress in understanding the mechanisms involved in the health effects of phenolics is limited because very little information is available regarding the existence of these compounds in human or animal fluids.In this study, a GC-MS method was developed for the simultaneous determination of various flavonoids and phenolic acids in human plasma.