Objective: To determine the content of m-aminoglutethimide, the key impurity in aminoglutethimide with an HPLC method.Methods: Chromatog. was performed on a Waters Spherlsorb column (4.6 mm × 150 mm, 5 μm), with a mixture of pH 5.0 acetate buffer: MeOH (75:25) as the mobile phase.The detection wavelength was 240 nm.Results: The content of m-aminoglutethimide in aminoglutethimide is < 1.0%.The calibration curve was linear at 0.025-0.150 μg (n = 5, r = 0.999 8), and the average rate of recovery was 100.7% (n = 5, relative standard deviation = 1.33%).Conclusion: The method is accurate, sensitive, reliable and could be used as the limit test of m-aminoglutethimide in aminoglutethimide.