A high performance liquid chromatographic procedure has been developed for the assay of a cefepime and metronidazole mixture in aqueous solution. The separation and quantitation were achieved on a phenyl column at ambient temperature using a mobile phase of 94.5:5.5 v/v water-acetonitrile containing 0.015 M pentane sulfonic acid sodium salt (adjusted to pH 3.4 with glacial acetic acid and then 4.0 with 45% potassium hydroxide) at a flow rate of 1.5 mL/min with detection of both analytes at 280 nm. The separation was achieved within 10 min with sensitivity in the ng/mL range for each analyte. The method showed linearity for cefepime and metronidazole in the 18.77 – 300.2 and 9.39 – 150.1 μg/mL ranges, respectively. Accuracy and precision were in the 0.52 – 2.40 and 0.63 – 2.77% ranges, respectively, for both analytes. The limits of detection for cefepime and metronidazole were 125 and 63 ng/mL, respectively, based on a signal to noise ratio of 3 and a 10 μL injection.