Fruit flies in the genus Anastrepha, especially the reproductive age females, are attracted to protein baits. Synthetic lures based on the principal components of protein degradation, especially ammonia along with acetic acid, were tested against three of the most economically important Anastrepha species. The results varied among the species, perhaps in part because of the different envionmental conditions where these pests are prevalent. In Mexico and Florida, A. ludens and A. suspensa, respectively, were caught in higher numbers by traps baited with synthetic lures containing ammonium acetate and putrescine. But, in the Dominican Republic where A. obliqua is the dominant pest, traps with whole aqueous protein baits outperformed the synthetic blends. Ideally, a single attractant formulation could be deployed by a regional crop protection program for detection of an array of pest fruit flies. Our results suggest that the optimal blend may vary among species and from one region to another.