The effect of lindane on numbers and community structure of oribatid mites was studied in northern Montana. Trees on five O.4-haplots were sprayed with lindane at 5.5 kg/ha (AI) in a simulated operational program to protect lodgepole pine from bark beetles. Sprayed plots and paired control plots were sampled before spray application and five times after treatment over a 2-yr period. Numbers of immature specimens changed more than numbers of adults. Both were Significantly depressed 113 after treatment. Two superfamilies were significantly affected after spraying. Of five measures of community structure, none demonstrated an effect; however, the powers of the statistical tests were quite low. The importance of statistical power in studies of effect of pesticides on nontarget species is discussed. Because the observed effects were short-lived and of relatively small amplitude, we conclude it is unlikely there is a lasting effect on the oribatid community.