We performed a retrospective review of data based on poison center exposure inquiries related to chlorpyrifos (CP) and the corresponding poison center-determined medical outcomes reported to the Toxic Exposure Surveillance System (TESS) of the American Association of Poison Control Centers. Ten y (1985-1994) of TESS data were obtained. Medical outcomes representing all inquiries, accidental/unintentional inquiries, and intentional/suicidal inquiries were tabulated. Published TESS data was also tabulated to allow comparison of CP exposure inquiries to all non-pharmaceutical and insecticides/pesticides exposure inquiries for like time periods. Frequency of antidote use, product sales data, CP-related fatality reports, and pertinent issues related to telephone derived surveillance data were also reviewed; 36, 183 CP exposure inquiries were identified. Of all CP exposure inquiries, 27, 473 (75.9%) were assessed as having no significant health consequences; 4,511 (12.5%) outcomes were judged unrelated and 2,980 (8.2%) were unable to be followed. Reported significant medical outcomes for the remaining exposure inquiries were moderate 1,092 (3.0%), major 119 (0.3%) and death 8 (0.02%). Considering only calls with outcomes judged causally related to CP, where a given level of effect could reasonably be determined, 95.8% (27,473/28,692) of these calls resulted in no significant health effects. Use of antidotes specific to organophosphates were infrequent [atropine, 1.0% (385) and 2-PAM, 0.5% (177) of all cases respectively]. Despite the number of reported CP exposure inquiries, relatively few resulted in outcomes of consequence. TESS data suggested that the majority of patients undergoing medical evaluation and/or treatment after a suspected CP exposure do not require specific antidotes. TESS data serves as a useful first step in evaluating product safety. Assessment of product toxicity requires additional investigation of reported adverse effects and circumstances related to the incident.