Purpose: Pyrethroid is an insecticide that produces moderate intoxication in mammals, with neither exposure to skin nor inhalation resulting in severe systemic manifestations. In 2005 we made a nationwide survey of agrichemical human intoxication. The object of this study is to analyze pyrethroid intoxications based on the 2005 survey. Methods: We prospectively collected data from 1 August 2005 to 31 July 2006 by a standard investigation protocol. We analyzed demographic data, exposure data (cause, amount, ingredients), clinical features, and courses. Results: A total of 125 cases of pyrethroid intoxication were surveyed. The mean patient age was $56.78{pm}16.158$ years old, and the mean amount ingested was $121.85{pm}110.732ml$. Patients were classified into four severity groups according to symptoms and mental status: the asymptomatic group (27 patients, 21.6%), the mild symptom group (48, 38.4%), the moderate symptom group (21, 16.8%), and the severe symptom group (7, 5.6%). There were statistically significant differences in mental status, severity, and mean ICU days between two groups. Admission days by severity grade for the asymptomatic, mild, moderate, and severe symptom groups were $5.49{pm}16.051,;3.65{pm}4.143,;4.59{pm}3.335,;and;8.14{pm}7.199days$, respectively (p=0.047). Conclusion: Nationwide surveillance was extremely telling in uncovering a high frequency of agrichemical intoxication in Korea. In pyrethroid intoxication, severity grading can be a useful prognostic tool.