Thirty-eight specimens of Oochoristica macallisteri sp. n. were recovered from the small intestines of 16 of 123 (13 %) side-blotched lizards, Ota stansburiana Baird et Girard from California, USA. Oochoristica macallisteri sp. n. belongs to a group of species of Oochoristica possessing fewer than 25 testes in a single cluster and circular suckers, namely, O. elongata, O. junkea, O. lygosnmae. O. lygosomalis, O. novaezealandae, O. parvngenitalis and O. sobolevi. The new species can be readily differentiated from the other species of this group by number of lobules of the ovary or number of proglottids and from other species from California by number of testes or shape of vitellarium.