The genus Phyllophaga (s. lato) in America north of Mexico embraces ca. 200 species in seven sub-genera ((P.) Phyllophaga, (P.) Phytalus, (P.) Listrochelus, (P.) Tostegoptera, (P.) Triodonyx, (P.) Cnemarachis, (P.) Chlaenobia). The taxonomic associations between these sub-genera have been a point of conflict among students of this genus for nearly 200 years. The relationships of the first five of these sub-genera are hypothesized using mtDNA sequences, male capture (sex attractant response) in vane traps when presented with a series of sex pheromones identified from several Phyllophaga species, and a comparison of genitalic groups. These results indicate that the monophyly of the sub-genus Phytalus as presently described is questionable. (P.) Phytalus obsoleta, although assigned to the sub-genus Phytalus on the basis of cleft tarsal claws, shares genitalic similarity, sex attractant responses and mtDNA sequence data with (P.) Phyllophaga crinita, a species without cleft claws. Those species in which males were captured exclusively in traps baited with the methyl esters of the essential amino acids L-valine and L-isoleucine form a monophyletic group encompassing the (P.) Phyllophaga (s. str.). The only two members of the sub-genus (P.) Tostegoptera, (P.) Tostegoptera lanceolata and (P.) Tostegoptera squamipilosa, form a monophyletic group based on genitalic similarities, mtDNA sequence, and male captures in the methyl ester of the essential amino acid L-leucine. This study demonstrates the utility in combining male responses to sex attractants with traditional characters for a more revealing analysis