In order to elucidate the possibility of diagnosis in soft tissue cysticercosis in case no parasite in it, immunohistochemical staining with antihuman IgG, IgM, and IgA and anticysticercus antibody in tissue section were carried out. Not only the differential counts of infiltrated plasma cells but also the parasite itself against to the anticysticercus antibody were observed. Materials stained immunohistochemically were consisted of 21 soft tissue cysticercosis with or without parasite. The results were as follows: 1) IgG producing plasma cells were most frequent (45.8+/-18.7) and followed by IgM (14.3+/-0.43) and (4.3+/-5.71). Number of IgG plasma cells were more frequently accompanied in the presence of cysticercus (55.9+/-17.7) than in the absence of parasite (39.7+/-17.1). 2) The mean+/-S.D. of plasma cells positive to the anticysticercus antibody were 28.2+/-18.7. And anticysticercus antibody producing plasma cells were more frequent in the presence of cysticercus (49.2+/-5.16) than in the absence of parasite (15.2+/-9.46). 3) Antigenicity of the cysticercus was strong in inner layer(#) followed by tegument(+) and fibrous layer(-). 4) Therefore, it could be suggested that antibody against to the cysticercus is mainly produced by IgG plasma cells and antigenicity of the worm is strong in the inner layer of cyst wall. In addition, there is a possibility of assisting the diagnosis of cysticercosis with anticysticercus antibody by immunohistochemically.