Effects of the gel preparation temperature T-prep and the initial monomer concentration c on the swelling and the porosity properties of poly(N-isopropylacrylamide) (PNIPA) networks are described. PNIPA networks were prepared by free-radical crosslinking copolymerization of N-isopropylacrylamide and N,N'-methylene(bis)acrylamide (BAAm) in aqueous solutions. The crosslinker (BAAm) concentration in the initial monomer mixture was kept constant at 30 wt %. It was shown that macroporous PNIPA networks with a stable porous structure can be prepared at T-prep = 22.5degreesC and at an initial monomer concentration c > 5 w/v %. The PNIPA networks contain pores of about 0.1 mum in radius, corresponding to the interstices between the microspheres. The experimental data also show collapse of the porous structure in PNIPA networks formed at higher temperatures.