Field trials were conducted to determine the potential use of corn steepwater, an acid-hydrolyzed corn product, as a liquid bait for the Caribbean fruit fly,Anastrepha suspensa(Loew), in Florida. Preference tests compared relative attractiveness among aqueous solutions of standard torula yeast plus sodium borate pellets or 10% steepwater (vol:vol) plus 1, 3, 5, and 10% (wt:vol) borax in traps. Total number of females trapped decreased from 474 in fresh bait solution to 197 and 154 in 2–3-d old and 4–6-d old bait solutions, respectively. When freshly prepared solutions were tested, the torula yeast-borax solution was the most attractive and the 10% steepwater with 1% borax the second most attractive bait formulation, capturing 45 and 23% of the trapped females, respectively. After 2–3 d of field-use, there was less discrimination among the baits, although the 10% steepwater with 1% borax and with 10% borax each captured 29% of the trapped flies. By the last 4–6 d of field use, the 10% steepwater with 1% borax was most preferred and captured 45% of the trapped flies. Dissections of subsamples of trapped females indicated that only 50% of the females from tortula yeast-borax traps were unmated, while 80–95% of the females caught in any of the steepwater traps were unmated. The addition of 1, 3, 5, and 10% borax increased the initial pH of the acidic steepwater to 5.95, 7.76, 8.44, and 8.76, respectively. The relative attractiveness of the 10% steepwater with 1% borax increased as this bait approached a neutral pH over the 6 d of field use.