The primary types of beetles (Coleoptera) in the C. A. Triplehorn Insect Collection at The Ohio State University are catalogued. Data on original combinations, current combinations, and type locality are verified and presented. A brief history of the collection is recounted. There are 200 primary types (172 holotypes, seven neotypes, one lectotype, 20 syntypes) from 28 families and eight countries in the collection. A total of 24 specimens labeled by others as primary types were confirmed as manuscript names and are presented in a separate list. The primary type of Luperaltica nitida Wilcox is presumed to be lost. The presumed holotype of Edrotes fossor Triplehorn was previously erroneously labeled, and a lectotype is designated from the paratype series.