Technical Abstract: This chapter, for a book on methods used to study pathogens of invertebrates, is a relatively nontechnical treatment of methods to prepare and observe specimens of fungal entomopathogens, and to identify the most common and important of these fungi to to the generic or, in many instances, the specific level. The key (1) includes all important variant stages in which these fungi may be collected, and (2) is written to be usable by those with little or no formal mycological training as well as by professional mycologists. The individual treatments of fungal genera provide explicit, illustrated lists of key diagnostic characters; this is an approach that has not been taken in any previous published treatment of fungal entomopathogens.