Phylogenetic relationships within the Aphidiinae, and between this and other subfamilies of Braconidae (Hymenoptera), were investigated using sequence data from three genes: elongation factor-1alpha, cytochrome b, and the second expansion segment of the 28S ribosomal subunit. Variation in both protein-coding genes was characterized by a high level of homoplasy, but analysis of the expansion segment--robust over a range of alignment methods and parameters-resolved some of the older divergences. Parsimony analysis of the combined data suggests the following tribal relationships: (Ephedrini + (Praini + (Aphidiini + Trioxini))). In addition, the cyclostome subfamilies were found to form a clade separate from the Aphidiinae, but relationships between the Aphidiinae and the noncyclostome braconids could not be resolved. The inferred phylogeny also supported a secondary loss of internal pupation within the Praini and a polyphyletic origin of endoparasitism within the Braconidae.