Trees in 3 southern pine beetle infestations were treated with one of 4 treatments of inhibitors of southern pine beetle aggregation behavior to determine their effects on beetle aggregation behavior. Brevicomin isomers and brevicomin isomers + verbenone reduced landing trap catch by 74 and 84%, respectively. These same compounds effected a 52 and 92% reduction in southern pine beetle galleries in treated trees. There was an increase in theIps avulsustrapped on the treated trees. Verbenone alone did not affect either southern pine beetle orI. avulsusactivity. None of the inhibitor treatments prevented the treated trees from succumbing to the southern pine beetle and/or possibleIpsattack. However, the reduction in both number and length of beetle galleries indicates that the brevicomin isomers and brevicomin isomers + verbenone could cause significant reduction in brood production. These results suggest the potential use of these compounds in reducing tree mortality by reducing brood production. The numbers and distribution of predaceous clerids,Thanasimus dubius(Say), on attacked trees were unaffected by the inhibitors.