The stoic nature of donkeys and mules can prove to be challenging for the practitioner who is tasked with diagnosing an illness or disease condition in these animals. Testing to obtain a specific diagnosis serves as a crucial tool for veterinarians who are examining sick donkeys and mules. Testing of both live and dead equids allows for the identification of pathogens, which can aid in the development of targeted prevention measures to reduce transmission in a group or herd. It can also assist in the detection of zoonotic disease agents, thereby allowing for appropriate post exposure or preventive measures to be implemented. Although a gross necropsy examination may provide all the answers that are needed surrounding the death of a donkey or mule, further diagnostic testing utilizing specimens collected from the necropsy may be warranted in many situations. These tests can only be properly performed and interpreted when the diagnostic specimens are collected appropriately. This chapter will describe the proper diagnostic specimens to collect from both live and dead equids in a variety of scenarios, for submission to a laboratory for testing. It will also describe the equipment and techniques required to perform a proper field necropsy.