Medicated feeds (pelleted or mash) containing guarantees of carbadox, furazolidone, nitrofurazone, and ethopabate are pretreated with water, extracted with 95% dimethylformamide overnight at room temperature, cleaned up on a column of alumina, and injected into a high pressure liquid chromatograph for quantitative measurement. Carbadox, nitrofurazone, and furazolidone can be separated; chromatograms show excellent baseline resolution, and results are in good agreement with colorimetric methods. The same extraction and cleanup can be used to improve colorimetric methods for furazolidone and nitrofurazone.