The impact of biological rodenticide Biorat on populations of rodents settled in some crops was determined; these crops are highly infested with Sigmodon hispidus, a very common vector in various Central American countries. The trapping technique and the appraisal of damages allowed to calculate the index of infestation which ranged from 75 to 90 percent in three crops. Twenty for to 36 kg of BIORAT were applied to 6 ha planted with Cucumis sativus (cucumber), Ipomoea batata (sweet potato) and Ananas comusus (pineapple). This action brought about that the rodent population in such crops reduced the potential damage and consequently, index of infestation was reduced by 94.6 to 98%; therefore, the residual population left amounted from 2 to 3.5%, meaning that damages were under the economic threshold. Generally speaking, the results were similar to those of other countries.