Conotrachelus nenupharHerbst (Coleoptera: Curculionidae), is a key pest of stone and pome fruits in North America. The behavioral response of adults of different physiological states (sex, age, diet, and mating status) to three commercially available synthetic lures, benzaldehyde (BZ) and plum essence (PE), the male-produced aggregation pheromone, grandisoic acid (GA), or their combinations, was studied in the laboratory. Four choice olfactometer bioassays demonstrated significant attraction of both sexes to PE lure. Both BZ and GA lures were not attractive to plum curculio when tested as commercially formulated. PE had higher release rate (1.51mg/hr) than BZ (0.36mg/hr) and GA (ca. 0.04mg/hr), suggesting that the higher attractiveness of PE may be due to its relatively higher release rates. Tests with combined lures showed a neutral effect of combining GA with PE and an inhibitory effect of combining BZ with PE. The physiological conditions of the weevils had no significant effect on their response to the lures. Olfactometer tests with pure 1,2,4-trichlorobenzene (TCB) confirmed that this compound was inhibitory to plum curculio. These results are discussed in relation to the contrasting field reports which implicated BZ + GA as an effective attractant for plum curculio.