We respond to Valle and Clark,(1) who assert that "conservation efforts may increase malaria burden in the Brazilian Amazon," because the relationship between forest cover and malaria incidence was stronger than the effect of the deforestation rate.(1) We contend that their conclusion is flawed because of limitations in their methodology that we discuss in detail. Most important are the exclusion of one-half the original data without a discussion of selection bias, the lack of model adjustment for either population growth or migration, and the crude classifications of land cover and protected areas that lead to aggregation bias.(1) Of greater significance, we stress the need for caution in the interpretation of data that could have profound effects on regional land use decisions.