The relative attractiveness of six commercially available protein hydrolysates and the influence of their concentration were studied in field cages by a release-capture method of laboratory-reared adult melon flies, Bactrocera cucurbitae (Coquillett). Buminal, Corn Steep Water, Hym-Lure, Pinnacle, Nulure and Solbait were tested on both sexes of the melon fly. Clear differences in attractiveness between the tested products were demonstrated. Solbait appeared to be the most effective protein hydrolysate while Pinnacle and Corn Steep Water showed promising results. Within the range 0.5-10%, a general tendency for an increase in effectiveness with increasing concentration was shown. Borax, which is commonly used as a preservative in food attractants, was tested as an adjuvant in association with several protein hydrolysates, and proved to be repellent to the melon fly. Different brewery yeast wastes were also tested as a protein source for melon fly bait. Some of them were reasonably effective, but their efficacy still needs to be improved. Alkalinization of the bait solution appeared to increase the attractiveness of these brewery yeast wastes. The results of this study will enable the selection of the most effective attractants for use in bait sprays to control the melon fly.