Transparent gels obtained from polyhydroxoaluminum (PHA) solutions on drying were transformed into activated alumina by heating. To obtain activated alumina with uniform pore size, different amounts of tetrapropylammonium chloride (TP) or tetrapentylammonium chloride (TPn) were added to PHA solutions prior to drying to form composite gels. The γ-alumina obtained from the composite gels with ≥40% TP content showed a sharp unimodal pore size distribution in the range of 3 to 4nm, depending on the heat treatment temperature in the range of 400 to 900°C. The γ-alumina thus obtained gave the largest pore volume of 0.30cm³·g^-1 at 600°C. On the other hand, the pore properties of the products obtained from the PHA-TPn composite gels were similar to those obtained from PHA gels without additives, giving a bimodal pore distribution and a small surface area. These results indicate that the pore size of γ-alumina can be precisely controlled by the heat treatment temperature using composite gels with ≥40% TP content.