Abstract: HPLC was applied to the determination of metronidazole, tindazole, ornidazole and secnidazole in cosmetics. The sample was extracted ultrasonically with a mixture of methanol and 0.1 mol·L-1 HCl solution (1+1) for 15min. C18 chromatographic column was used as stationary phase, and a mixture of methanol, acetonitrile and water (7+1+2) was used as mobile phase. UV-detection at 315 nm was adopted in the determination. Linear relationships between values of peak area and mass concentration of the 4 nitroimidazoles were kept in definite ranges, with detection limits (3S/N) and lower limits of determination (10S/N) less than 10 mg·kg-1 and 30 mg·kg-1 respectively. On the base of a blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 93.8%-104% with RSD′s (n=6) in the range of 0.2%-4.1%.