Biopsy of muscle and nerve is an essential component of the diagnostic plan for animals with suspected neuromuscular disease. This article includes descriptions of the biopsy procedures and information regarding appropriate biopsy site selection and correct handling and processing of the tissues. The normal and pathological appearance of muscle and nerve using routine histochemical and histological techniques are described and illustrated emphasizing the basic myopathic and neuropathic responses of the neuromuscular system.