This communication is presented with two objectives in mind. The first objective is to provide an introduction to personnel monitoring of occupational exposure to pesticides for those who are not familiar with this field of investigation. The second objective is to stimulate discussion, which will result in the formation of recommendations for research necessary for material improvement of exposure assessment. Two principles were observed in the development of the methods currently used at Wenatchee and should be preserved by anyone considering modifications. First, all possible care was taken to ensure that any error was on the side of safety, that is, it would result in overestimation of exposure. Second, no technique was considered acceptable if it would increase a test subject's exposure over what he would receive under normal working conditions.