Eosinophilic myositis is a relatively rare condition of cattle and sheep in which individual muscles or groups of muscles may be involved, or the lesions may be widespread through all muscles, including the heart The condition has been seen in pigs, and a case has been described in a monkey. A similar pathological entity confined to the muscles of mastication has been reported in dogs. Although Sarcocystis has often been implicated in ruminants and pigs, the specific cause of this condition remains unknown. We report here a case of generalized eosinophilic myositis with simultaneous infestation with Sarcocystis in a raccoon, and the results of a survey on the prevalence of muscle parasites in raccoons. Between July 1985 and February 1988, l01 adult raccoons of both sexes were examined at the Laboratory of Large Animal Pathology, University of Pennsylvania, Kennett Square, Pennsylvania. These raccoons were either suspect rabies cases (from Pennsylvania) or were part of a larger study on the development of an oral vaccinia-rabies glycoprotein recombinant viral vaccine (from Ohio).’ Whenever possible, prior to euthanasia of the raccoons, blood samples were obtained for routine hematology and blood chemistry. At the time of necropsy, a sample of cerebrospinal fluid (CSF) was obtained (within 15 min of euthanasia) for cytological examination. Also at the time of necropsy, besides other tissue samples, striated muscle samples from 5 different organs (heart, tongue, diaphragm, proximal esophagus, and masseter muscle) were fixed in 10% phosphate-buffered formalin. Examination of these muscles forms the basis of the present study. The tissues were processed routinely for histopathology for examination by light microscopy. Selected sections were stained with periodic acid-Schiff (PAS) and hematoxylin and eosin (HE). Samples of striated muscles were taken for electron microscopy, the results of which have been published elsewhere. Gross lesions were seen in the muscles of only 1 of the raccoons-an adult female used in the vaccine trial. The lesions consisted of numerous small (to 3 mm wide), pale white, streaklike to oval granulomatous areas, which were numerous and more prominent on the diaphragm and on the muscles of the abdomen and the thigh (Fig. 1). Histological examination of the striated muscles from different anatomical sites revealed presence of Sarcocystis (48 cases), Trichinella (3 cases), and Hepatozoon (in 1 raccoon). Heart muscle was the least likely tissue (12% positive), whereas the tongue (37% positive) was the most common place for