The biotechnology reached the principal link of the soy complex, that is, the producers. The GMO soybean promotes the reduction of the necessary amount of herbicide and the cost of production. The objective of this study was to determine and compare the average costs incurred into the production of conventional and the new technology for the South Mato Grosso State of the harvest 2004/05, through primary data, obtained for field research. In the present work it is presented the methodology adopted for the formation of the data base and for the countable structure properly said. Through the analysis of the data base it was possible to observe that the cost of the GMO is approximately 14.8% less than the conventional one.