A phylogenetic analysis was performed on 13 species of digenetic trematodes in the Macroderoididae, including 10 species of Alloglossidium, 2 species of Alloglossoides, and Hirudicolotrema richardsoni. The evolution of the unusual life-cycle patterns in the group was assessed in light of the proposed phylogeny. The results support previous hypotheses that taxa with a 3-host life cycle involving catfish as definitive hosts are basal to taxa with a 2-host life cycle involving invertebrates such as crustaceans and leeches as definitive hosts. Our results also strongly suggest that species maturing in leeches evolved from an ancestor that matured in crustaceans. Our phylogeny places Alloglossoides and Hirudicolotrema within Alloglossidium, showing Alloglossidium to be paraphyletic. To achieve a natural classification, Alloglossoides and Hirudicolotrema are synonymized with Alloglossidium, and a revised generic diagnosis for Alloglossidium is given.