Calcareous corpuscles, known as mineral concretions in Platyhelminthes, may have special biological functions. In the present study we succeeded in the quantitative separation of calcareous corpuscles in plerocercoids of Spirometra mansoni (sparganum) using Ficoll. Purified calcareous corpuscles were reacted with crude extracts of Platyhelminthes, including sparganum. Proteins commonly binding to calcareous corpuscles were molecules of 10, 17, 22, and 35 kDa. A 95-kDa molecule was found to bind specifically in cystic fluid of Cysticercus cellulosae, as was a 40-kDa protein in crude extracts of Taenia saginata and a 27-kDa molecule in crude extracts of Paragonimus westermani and Clonorchis sinensis, respectively. This finding suggests that calcareous corpuscles might have a binding activity to proteins in crude extracts of sparganum.