To investigate neurophysiological effects of low-level exposure to foliar organophosphate residues during one season among agricultural workers, the authors performed a cross-sectional study of 67 Hispanic farm workers and 68 age-, gender-, ethnicity-, and education-matched reference subjects. The neurophysiological examination included sensory and motor nerve conduction and neuromuscular junction testing. Erythrocyte cholinesterase activity was measured at the time of examination. No statistically significant neurophysiological differences between the exposed and reference groups were observed. Farm workers and reference subjects had similar sensory nerve latency and amplitude (sural), motor nerve conduction velocity (ulnar), and neuromuscular junction function (ulnar). No relationship between duration of exposure during the season and electrophysiological measures of nerve function was found. Exposure of farm workers to the low levels of organophosphate pesticides during one season experienced by farm workers in this study was not associated with impaired peripheral neurophysiological function.