ABSTRACT: Enterocytozoon salmonis, an intranuclear micro-sporean of salmonid fishes, is often difficult to visualize by light microscopy. In paraffin sections stained with hematoxylin and eosin (H&AMPE), the parasite appears as a light staining sphere within the nucleus, and can easily be confused with nucleoli or nuclear vacuoles. Furthermore, the spores of E. salmonis are very small and do not form large aggregates, and thus are not easily identified in sections or wet mounts. The Warthin-Starry stain combined with H&AMPE dramatically enhances the detection of the parasite in tissue sections. Using this method, prespore stages stain light brown to black, and spores stain dark brown or black.