Definitive diagnosis of microsporidial infection relies on observing microsporidia in biopsy tissue, bodily fluid specimens, or stool examined by transmission electron microscopy. This method lacks sensitivity when performed on stool and is a very laborious and specialized procedure. Detection of microsporidia by light microscopic examination of stained stool specimens from patients with gastrointestinal infection allows rapid diagnosis in a routine clinical microbiology laboratory. Because microsporidia are not detected in traditional ova and parasite examinations of stool specimens, modifications of the trichrome stain are now available for the detection of microsporidia in stool specimens. The currently accepted standard protocol for modified trichrome staining of microsporidia includes a 1-hour incubation in the modified trichrome stain. We hope to demonstrate that a rapid staining method, which includes shorter exposure to the modified trichrome stain, will provide comparable or superior results. A device that allows stain to be maintained at 50 degrees to 60 degrees C will be used in this effort to provide a rapid and easily interpretable staining method. We will participate in an international multicenter diagnostic study to compare the sensitivity and specificity of the modified trichrome stain with the polymerase chain reaction. We will receive 50 specimens (both positive and negative) to stain with the modified trichrome stain and examine them for the presence of microsporidial spores. The data from the 12 participating laboratories will be combined and a manuscript prepared for publication.