This study quantifies private and social levels of agricultural pesticide overuse by combining an abatement function approach to estimate the marginal benefits of pesticide use with the Pesticide Environmental Accounting (PEA) tool to estimate marginal social costs. We applied the method to one intensive vegetable production system in the mountainous north of Thailand by using farm and plot level survey data. We find that the exponential specification for the abatement effect of pesticides gives more realistic outcomes than the logistic specification. Based on an exponential specification, we estimate that private overuse is 78-79% of the applied quantify of pesticides, while social overuse is 79-80%. The difference between private and social overuse is small as the exponential form reaches an optimum at a relatively low level of pesticide use.