A simple, rapid method, based on high-performance liquid chromatography, is described for the assay of amprolium in poultry feedingstuffs. The drug is extracted from the feed by use of an ethanol-water (3 + 1 V/V) mixture and aliquots of this solution are chromatographed on a silica gel column, using a methanolic mobile phase containing ammonium nitrate and ammonia solution. The method is applicable to feedingstuffs containing at least 5 mg kg–1 of amprolium. The constituents of grass (10%m/m) and fish (10%m/m) meals and the presence of pyrimethamine, ethopabate, sulphaquinoxaline, arsanilic acid, nitrovin, nifursol, dimetridazole, virginiamycin and vitamins A, D3 and E do not interfere in the analysis.