Ginger (Zingiber officinale Roscoe) is widely used as a common condiment for a variety of foods and beverages. In addition to its extensive utilization as a spice, the fresh or the processed rhizome is a useful crude drug in traditional Chinese medicine. It is considered to possess stomachic, carminative, stimulant, diuretic and antiemetic properties. Chemical studies on the pungent principles of ginger have been carried out by a number of investigators, and 6-gingerol and 6-shogaol as a major pungent substance have been isolated. In this study, the constituents inhibiting a drug metabolizing enzyme CYP3A4 from ginger were investigated. CYP3A4 is responsible for drug metabolism as heme-containing monooxygenases. As a result of experiment, 10-gingerol (lC$_{50}$ 5.75$mu$M) isolated from EtOAc extract of ginger showed remarkable inhibitory activity compared to 6-gingerol ($IC_{50}$/ 14.56 $mu$M) and zingerone ($IC_{50}$/ 379.63 $mu$M). This paper describes the isolation, structure elucidation, and CYP3A4 inhibitory activity of these compounds. The structure of the compounds were identified by instrumental analysis such as LC-mass spectrometer and NMR.R.