The rapid identification of residues of mammalian materials in animal feedstuffs is important for the effective control of feed as a potential source of transmission of bovine spongiform encephalopathy (BSE). It is included in the monitoring program developed to avoid the appearance of this disease. In the present work a PCR analysis was tested for the detection of mammalian residues (bovine, caprine, ovine and porcine). The DNA extraction method utilised guanidium thiocianate, and primers flanking a conserved region of mitochondrial DNA were synthesized for each species. PCR tests were specific for each species and allowed detection in feedstuffs of levels as low as 1% of bovine DNA and 1.5% of ovine, caprine and porcine DNA. These PCR tests may allow the rapid detection of residues of these species constituting a powerful tool against BSE