The objective of this work was to evaluate the efficiency of two methods used to estimate of grains yield on commercial corn farms. The Reetz method, developed at the University of Illinois, in the United States, and the Emater–MG method, used in Brazilian corn fields were appraised. The efficiency of the methods was analyzed in three areas in two location of Minas Gerais State on Brazil. For obtaining of the estimated productivities, the areas were divided in 4 plots, six portions being harvested per plot in the first area and one portion per plot in the other area. Each portion was made up of 7 sub-samples of 4 m˛ with 3 ears of corn each, distributed in 4 lines of 10 m. For the Reetz method, the number of ears of corn in 4m2, the number of rows of grain and the number of grains per row were used in the calculation expression. For the Emater method, the spacing among lines, number of ears of corn in 10 m and the average grain weight per ear of corn was used. With the variance components of each analysis, variance functions were determined in accordance with the number of portions and sub-samples for subsequent determination of intervals of 95% confidence of the estimated average productivity for the methods, with the intention of verifying if these contained the real productivities of the locals. It is concluded that the validity of the estimated productivities depends on the number of portions and sub-samples considered. The Emater method is useful for comparisons among productivities of different areas. The number of ears of corn sampled per portion that has been recommended by the Emater method can be reduced by half. The Reetz method needs to be adapted to hybrid groups with similar characteristics.