Nucleotide sequences of the Cryptosporidium oocyst wall protein (COWP) gene were obtained from various Cryptosporidium spp, (C. wrairi, C. felis, C. meleagridis, C, baileyi, C, andersoni, C. muris, and C,serpentis) and C, parvum genotypes (human, bovine, monkey, marsupial, ferret, mouse, pig, and dog). Significant diversity was observed among species and genotypes in the primer and target regions of a popular diagnostic PCR, These results provide useful information for COWP-based molecular differentiation of Cryptosporidium spp, and genotypes.