In this study, alumina precursors were prepared in three different ways and were converted into three different alumina powders (A12O3) by calcination. The precipitation methods of the alumina precursors were as follows: i) Addition in excess of a 25% NH3 solution dropwise for two hours, to a boiling 0.08 M A12(SO4)3 solution which was already buffered by NH3 / NH4C1. ii) Boiling for two hours a 0.006 M A12(SO4)3 solution which contains C2H |(CO()[[)2. \H4C1 and (NH^CO. iii) Boiling for two hours a 0.2 M A12(SO4)3 solution which contains excess (NH2)2CO. hi orda- to find out the effect of the followed procedure on the pore structure, the following determinations were realized. The powder shapes and sizes were determined by electron microscopy. The specific surface areas and the adsorption heats of these powders were calculated from the adsorption data. The mesopore size distribution curves were plotted by using the desorption data. The specific micropore, mesopore and micropore-mesopore volumes were determined by extrapolating these curves. Finally, the dependence of the pore structure rm the procedure of preparation w'as discussed in detail.