Gel electrophoresis and Western blotting were used to investigate the recognition of Cryptosporidium parvum oocyst antigens by sera from asymptomatic C. parvum-seropositive cattle with or without coccidian oocysts in their faeces (C. parvum or/and Eimeria spp.). Most sera from coprologically C. parvum-positive animals (71%) recognized fractions in the 17-20 kDa range; these fractions were not recognized by sera from coprologically negative animals. In addition, most sera with antibodies to C. parvum (whether from coprologically positive or negative animals) showed moderate or strong reaction with antigenic fractions in the 47-49.5 kDa range (43%) and the 56.5-69 kDa range (80%).