Thermosensitive porous, cylindrical gel was synthesized by radical polymerization of N,N-diethylacrylamide (DEAA) as primary monomer and N,N′-methylenebisacrylamide as cross-linker. The synthesis was done at various temperatures above the LCST of poly-DEAA, about 32°C. The pore size distributions of these gels were measured by the solute exclusion method, and the swelling behavior of these gels was investigated. The volume fraction of the pores larger than 100 nm remarkably increased by synthesizing above 40°C. In other words, the porous structure developed. The gel synthesized at 37°C, i.e. near the LCST of poly-DEAA, largely deformed in the swelling process. On the other hand, the gels synthesized at 50°C swelled without deformation, in other words, retaining the cylindrical shape, and the swelling rate was inversely proportional to the square of the diameter of the gel. These swelling behaviors were discussed from the pore size distribution and the elastic modulus of these gels.