Histologic samples representing the 8 different microsporidia were obtained from the case files of the Zebrafish International Resource Center (Eugene, OR), Oregon State University Department of Microbiology (Corvallis, OR), University of California-Davis School of Veterinary Medicine (Davis, CA) and the Centre for Environment, Fisheries and Aquaculture Science (Weymouth Laboratory, UK). The histologic samples were comprised of six different teleost fishes, Mitten crab (Eriocheir sinensis) and a mussel (Mytilus sp.) that had been previously diagnosed with microsporidian infections. 10% neutral buffered formalin and Dietrich’s fixative were used for preservation of fish tissues and sea water Davidson’s fixative for mussel and mitten crab. Five serial sections, cut at 4 µm and deparaffinized, were made from each of the selected tissue blocks. These tissue sections were then stained with H&E and a special stain panel of Luna, Gram, Fite’s acid-fast and Giemsa stains. Luna and Gram stains were performed using Luna’s method for erythrocytes and eosinophil granules (Luna 1968 pages 111–112) and the Accustain™ Gram stain for tissue kit (HT90T, Sigma-Aldrich). Fite’s acid-fast and Giemsa stains were employed using Fite’s method for acid fast organisms (Luna 1968 pages 217–218) and May-Grunwald Giemsa method (Luna 1968 pages 121–122). Slides were evaluated for routine histologic features, presence of microsporidian organisms, detection of microsporidian spores by special stains, fidelity of staining for each of the special stains, amount of background stain and artifacts.