ABSTRACT. It has been shown that certain slow neurological diseases such as bovine spongiform encephalopathy (also known as "mad cow" disease) could be transmitted through contaminated food intake by animals; therefore, the examination of meat components in commercial feeds is important for the control of the disease in public health. The combination of polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs) technique was applied to examine the meat components in dog and cat commercial feeds. The partial nucleotide sequence (359 bp) of animal mitochondrial cytochrome b (cytb, CYT) gene was amplified by PCR and then digested with restriction enzyme Alu I or Mbo I. In this work, eight brands of commercial dog and cat feeds available in Taiwan were examined. All brands of dog feeds that were tested contained meat from four different animals (cattle, pig, goat and chicken). In cat feeds, the chicken meat was found in five out of eight brands. KEY WORDS: BSE, cyt b gene, dog and cat commercial diet, PCR, polymorphism.