In the eradication therapy of Helicobacter pylori changes of antibiotics as these concentrations or amount in the stomach after oral administration were not clear.A simple and accurate method for determining the concentration of metronidazole(MTZ) in homogenate of rat stomach was developed in order to obtain basic data to design a pharmaceutical preparation having targeting ability to the surface of gastric-mucosa.This method included a deproteinization process by methanol,separation with reversed-phase high-performance liquid chromatography,and detection with an ultraviolet wavelength of 370 nm.Regression analysis showed that the method was linear over a standard curve range from 5 μg/mL to 2000 μg/mL.The inter-day precision and accuracy values between the ranges were 5.0% or better and -7.5 to 5.2%,respectively.The newly developed method was applied to an analysis of gastric samples after oral administration of MTZ at a dose of 5 mg/kg.It was found that the residual MTZ in the stomach was determined within 5 h after dosing.This method is useful for monitoring MTZ in stomach after its oral administration to rats. In the eradication therapy of Helicobacter pylori changes of antibiotics as these concentrations or amount in the stomach after oral administration were not clear. A simple and accurate method for determining the concentration of metronidazole (MTZ) in homogenate of rat stomach was developed in order to obtain basic data to design a pharmaceutical preparation having targeting ability to the surface of gastric-mucosa. This method includes a deproteinization process by methanol, separation with reversed-phase high-performance liquid chromatography, and detection with an ultraviolet wavelength of 370 nm. showed that the method was linear over a standard curve range from 5 μg / mL to 2000 μg / mL. The inter-day precision and accuracy values ​​between the ranges were 5.0% or better and -7.5 to 5.2%, respectively. method was applied to an analysis of gastric samples after oral administration of MTZ at a dose of 5 mg / kg .It was found that the residual MTZ in the stom ach was determined within 5 h after dosing.This method is useful for monitoring MTZ in stomach after its oral administration to rats.