The mating calls of three members of the “regularis group” of toads (Anura: Bufonidae) that are sympatric in part of South Africa are examined. A naturally occurring population of hybrid toads from Pretoria (South Africa) has previously been described as representing an intergrading between Bufo garmani Meek and Bufo rangeri Hewitt. Examination of the mating calls of these toads provides little evidence of intergrading between Bufo rangeri and Bufo garmani, and indicates the involvement of Bufo regularis Reuss in the hybridization. The mating calls of the hybrids are varied, and are structurally intermediate between those of the parental species. Mating call parameters are found to be useful in separating forms that are difficult to distinguish on morphological grounds alone. They are further found to be a sensitive non-morphological means of ascertaining the affinities of naturally occurring hybrid toads.