Tests were conducted on White Leghorn chickens to evaluate the acaricidal action of malathion dust against Bdellonyssus sylviarum. No mites were found on caged birds treated with a 4% malathion dust up to 4 weeks following treatment. A 4% dust applied to the litter and nests at the rate of 1 lb./20 sq. ft. effectively controlled this mite. No effect on flavor was detected in eggs laid by hens fed on a diet containing 50 ppm malathion. Daily records kept by poultrymen indicated that treatments had no effect on egg production or hate liability.