Male Metamasius spinolae (Gylh.) produce several volatile compounds that are likely constituents of its aggregation pheromone. These compounds were identified by volatile collections and gas chromatography (GC), followed by coupled gas chromatography-mass spectrometry (GC-MS), as 2-methyl-4-heptanone [1], 6-methyl-2hepten-4-one [2], and 2-hydroxy-2-methyl-4-heptanone [3]. Preliminary field experiments using synthetic racemates of these compounds showed that significantly more adult cactus weevils were caught in traps baited with the major single compound three or the 2 3 binary combination than in unbaited control traps. However, highest trap efficacy occurred with the 1 2 binary combination and a blend of all three synthetic compounds plus prickly pear. Potential uses for the cactus weevil pheromone and possible ways to increase trap captures are discussed.