The aim of this study was to determine the effect of different sized aggregates on runoff, sediment by runoff, and by splash with simulated rainfall. A soil sample which is known and well aggregated, was taken from the Agriculture Faculty's Research Field of Ege University, and passed through different sieves (2520 mm, 20-16 mm, 16-10 mm, 10-5 mm, 5-2 mm, 2-1 mm, and 1-0.2 mm) to establish 7 grouping. The sieved soil samples were placed in the erosion trays (30x30 cm), and simulated rainfall (65 mm h(-1)) was applied to the trays for 1 hour. According to the results of the simulated rainfall experiments, the aggregate sizes were found very effective on runoff (p = 0.0001; r = -0.420**), sediment by runoff (p = 0.0001; r = 0.980**), water resistance aggregate stability (p = 0.0001; r = 0.840**), mean weight diameter (p = 0.041; r = 0.550*), and aggregate index (p = 0.0001; r = 0.867**), significantly. No correlation was found between the aggregate sizes and sediment by splash linearly but polynomial relationships were found between the aggregate sizes and sediment by splash in the study.