The Pathobiology Division of the Northeast Fisheries Center, National Marine Fisheries Service, has conducted studies on diseases of marine fishes, crustaceans, and mollusks for many years. Although these studies have implicated a variety of scientific disciplines, they have emphasized the use of histopathology in disease diagnosis. Histologic observations are not a panacea for the diagnostician, however, they permit an assessment of the host response and frequently the identity of the inciting agent. With many species of fish and shellfish, individual animals readily can be sacrificed and disease diagnosis based on histologic criteria is feasible. Host responses such as inflammation, degeneration, necrosis, hyperplasia, and neoplasia have been observed in a variety of diseases, centralized collection of microslides depicting lesions in tissues of marine fishes, crustaceans, and mollusks would provide study material for a wide variety of users. Microslide reference collections depicting lesions of infectious and non-infectious diseases are available for human and veterinary pathologists. The National Registry of Marine Pathology intends to acquire and accession microslides and other relevant materials depicting histologic lesions of marine fishes, crustaceans, and mollusks; the materials will be available for use by all interested users.