(NIOSH/CDC, 1993-2000) The overall goal of this study was to determine whether farm workers who thin fruit trees exhibit neurological changes following one season of exposure to low levels of organophosphorus insecticides compared to workers who were not exposed. Data were collected 97 in follow-up testing. A wide ranging number of tests, including peripheral and central nervous system function, were applied to both groups. Cholinesterase was measured both after the exposure season and after the period of non-exposure. Cross-sectional analysis of peripheral neurological outcomes after exposure revealed that there were no significant differences between exposed and non-exposed farm workers.