The proteocephalid tapeworm Proteocephalus torulosus (Batsch, 1786) exhibited a marked seasonality in its occurrence and maturation in barbel (Barbus harhus L.) from the Jihlava River, South Moravia, Czech Republic. Recruitment took place in winter and early spring, growth and maturation in spring and gravid worms left the fish hosts in May; during summer and autumn, the parasite was almost absent from the fish population. Parasite burden was related to fish size, with larger barbel being more heavily infected than smaller ones.