A contingent valuation approach to assess the health effects of chemical pesticides among Nicaraguan vegetable farmers is presented. Farmers' valuation of health is measured as their willingness to pay (WTP) for low-toxicity pesticides. Results show that farmers are willing to spend an additional amount of about 28% of current pesticide expenditure for avoiding health risks. The validity of results is established in scope tests and with a two-step regression model. WTP depends on farmers' experience with poisoning, income variables, and current exposure to pesticides. The results can help in designing rural health policies and in the formulation of programmes aiming to reduce the negative effects of pesticides.