Nanocrystalline boehmite[gamma-AlO(OH)] is a cost-effective material for the production of gamma-Al2O3 finding many industrial applications as catalyst or catalyst support, membranes and adsorbents. Therefore the effects of experimental variables in the preparation process of bohemite[gamma-AlO(OH)] sol were investigated in order to control the microstructure of gamma-Al2O3 particles in this study. Using aluminum isopropoxide as a precursor, gamma-AlO(OH) sol solution was prepared through the process of hydrolysis/condensation, aging, peptization and then gamma-Al2O3 particles were manufactured at high temperature through thermal treatment. As a result of this study, aging process among the sol preparation steps had an importance effect upon the crystallinity and microstructure of gamma-AlO(OH). And the microstructure of gamma-AlO(OH) particles controlled by aging had an influence upon the microstructure of gamma-Al2O3 particles such as specific surface area and pore size distribution. Hence, it could be known that the aging process was the most important step to control the microstructure of gamma-Al2O3 particles.