Nerolic acid, the second most abundant compound in the Nasonov pheromone of the honey bee,Apis melliferaL., was investigated to determine its importance as a component in synthetic attractants for honey bees of Africanized and European populations. Both populations of bees preferred synthetic pheromone blends containing nerolic acid in combination with citral and geraniol to those containing only citral and geraniol. These findings indicate that honey bee swarms of both Africanized and European populations recognize and respond in the same manner to synthetic Nasonov pheromone, and that nerolic acid exerts an important synergistic effect on the attractiveness of other Nasonov components. Nest cavity shape, tapered cylinder versus rectangular prism, apparently is not an important factor in cavity acceptance by honey bee swarms.