Use of disparlure to disrupt mating of low-density populations of gypsy moths,Porthetria dispar(L.), was tested in central Massachusetts in 1974. In one area with a naturally low population, disparlure in slow-release microencapsulated form was applied to 2.6-km2plots at the following rates: 5 g lure/ha, 2 consecutive treatments each at 10 g lure/ha 2½ wk apart, and 20 g lure/ha; a 4th plot served as an untreated control. Results obtained by treatment with 5 g lure/ha were considered inadequate, mating success of exposed females was reduced 47% compared with the control; male captures in monitor traps and post-treatment egg-mass counts also indicated ca. 50% control. Treatments with the higher dosages were more successful: mating success of exposed females was reduced 94–97%, and male captures and post-treatment egg-mass counts were also markedly suppressed.In a 2nd area, 2 treatments with insecticide were applied to a 6-km2island in the Quabbin Reservoir to reduce its potentially high gypsy moth population to a low level. One-third of the island received no further treatment, ⅓ was treated once with 20 g lure/ha as microcapsules, and ⅓ was treated by mass trapping with 25 high potency disparlure-baited traps/ha. The 3 treatments all showed the same degree of mating by exposed females, 2.4–3.2% relative to mating on an untreated (control) island, on which mating was 85.4%, despite a low initial population. Captures in monitor traps totalled 14 in the area treated only with insecticide compared with 5 each in the other 2 areas and 467 in the untreated control. Although egg-mass counts were low in all areas, none were found in the area treated with both insecticide and microencapsulated disparlure.In both areas, high potency monitor traps showed promise as a means of measuring effectiveness of treatment within disparlure-treated areas.The 1974 results strongly indicate that the air-permeation technique employing slowrelease encapsulated disparlure at the rate of 20 g lure/ha is effective in reducing mating success in low-level infestations or in infestations reduced to a low level with an insecticide.