Field tests of variations in concentrations of the 4 components of grandlure, the pheromone of the boll weevil,Anthonomus grandisBoheman, showed that increased percentages of alcohols (and thereby decreased percentages of aldehydes) significantly improved performance. One alcohol was more important than the other in determining activity, but both alcohols must be present with small amounts of the aldehydes for maximum effectiveness. Captures of boll weevils increased only slightly when doses were increased above 3 mg.