Due to the increasing consumption of eggplant (Solanum melongena L.), research should be carried out with this horticultural species aiming at providing technical recommendations for increasing production and quality of fruits. The aim of this study was to estimate the plot and sample size, as well the number of replications suitable for eggplant trials. Two uniformity trials were performed with eggplant in a plastic tunnel. The fresh fruit weight and the total number of fruits were assessed in each basic unit and in each harvest. The harvests were analyzed individually and grouped. Heterogeneity was found among crop rows and individual harvests within the same row. However, when the harvests were grouped, this fact was not observed. When the harvests are grouped, there was a reduction in plot size and sample needed the grouping of six harvests presented the smallest sample size and plot size. The plot size is five plants, the sample is nine plants in the direction of the crop row with a half-range of the 20% confidence interval. Aiming at achieving a minimum-significant difference in the Tukey’s test of 30% of treatment mean, three replications with five plants each plot is needed.