We studied the frequency of intraspecific brood parasitism and physical transfer of eggs between nests in colonially nesting Cave Swallows (Petrochelidon fulva) and Cliff Swallows (P. pyrrhonota) in south Texas in 2001. Although the eggs of the two species look similar, frequency of brood parasitism in each species was unaffected by presence of the other species, which suggests that the parasitism we observed was largely by conspecifics. We detected brood parasitism in 4.6–5.0% of Cave Swallow nests and in 10.7–11.9% of Cliff Swallow nests. Brood parasitism was not significantly related to colony size in either species, to eventual success of the host nest, or to overall colony nesting success (a measure of environmental risk). We detected evidence of physical transfer of eggs in 0.7–2.0% of nests of these species. Cliff Swallows parasitized nests more often than Cave Swallows, but the frequencies of brood parasitism and egg transfer in the two species in south Texas appeared broadly comparable to those reported for Cliff Swallows in Nebraska, despite geographic differences in habitat, seasonality, breeding phenology, and levels of sociality between the populations.