Enterobius nycticebi Baylis, 1928 and E. callithricis Solomon, 1933 are briefly redescribed and the oxyurid parasites of primates are discussed, additional morphological evidence being presented on many of them when necessary. The parasites are regrouped into two genera, with two subgenera each, thus: Enterobius Leach, 1853 with Enterobius and Protenterobius subgen. nov. (type species E. nycticebi); Trypanoxyuris Vevers, 1923 with Trypanoxyuris and Paraoxyuronema Artigas, 1937. A trend from a three-lipped mouth opening to a two-lipped is demonstrated within the genus Trypanoxyuris and a trend from a “doubled” to “single” spicule is demonstrated within Enterobius. It is pointed out that although the trend in Enterobius parallels the phylogeny of the hosts in part it does not necessarily establish a phylogeny particularly as there are relatively few records of the parasites. This is clearly demonstrated by recording from which of the genera of living primates oxyurid parasites have been reported. It is argued that “Cameron's Hypothesis”—one species of parasite (Enterobius or Trypanoxyuris): one genus of host—appears to hold good in the wild and that there is a tendency in the genus Enterobius for the parasites most like the parasites of man to occur in the hosts phylogenetically nearest man. The subfamily Oxyurinae is reviewed and two tribes, Oxyurini and Heteroxynematini, are recognized. It is reported that Callistoura brygooi Chabaud and Petter, 1958 does not have a spicule and that the structure described by Chabaud and Petter as such is a modified gubernaculum similar to that found in Ozolaimus and related genera. The great similarity between the male tail of C. brygooi and Ozolaimus is noted and it is suggested that Callistoura should be treated as a genus incertae sedis until a full study of the subfamily Pharyngodoninae, to which it is clearly related, can be undertaken. Several new synonyms are demonstrated, thus: Buckleyenterobius deniata Sandosham, 1950=Enterobius lemuris Baer, 1935; Oxyuris parallela Linstow, 1908=O. polyoon Linstow, 1909 and is referred to Enterobius; Oxyuris armata Kreis, 1940=Primasubulura distans (Rudolphi, 1819).