Almost in all vegetation types exists species that can cause toxicity to the cattle grazing. Poisonings cause very diverse problems in the cattle being able to affect the reproduction, weight gains, and even death. These problems cause economic losses in cattle industry that is necessary to quantify but very difficult to do so. Sonora has been diagnosed with overgrazed rangelands which is pronounced in deterioration that diminishes the desirable species and increases the undesirable ones, within these are the toxic plants. There have been identified 181 species that are toxic and within these there are 59 species that cattle consumes and cause problems. Based in this, the present study was planned with the purpose of trying to estimate the economic impact that toxic plants cause on cattle productivity in Sonora. Diverse sources of information were used for the elaboration of analysis and calculations that could come near to the quantification of the economic effects. The methodology described by Nielsen . (1990) was used for the estimation of these losses. The results show that a conservative estimation of the economic effect of these plants on the Sonoran rangelands can represent a loss of almost 90 million pesos annually.