DNA hydrogels were prepared from aqueous solutions of double-stranded DNA (about 2000 base pairs long) by physical and chemical means. Physical gels were obtained via denaturationrenaturation cycle of 5% aqueous DNA solutions between 25 and 90 degrees C. Although physical DNA gels exhibit a high modulus of elasticity, the crosslinks holding the DNA network together are destroyed during the expansion of gels in water or in dilute salt solutions. It was shown that these gels can be used for the controlled release of DNA in aqueous media. Chemical DNA gels formed using ethylene glycol diglycidyl ether crosslinker are stable in water with a wide range of swelling ratios that could be adjusted by the amount of DNA at the gel preparation. Swelling behavior of chemical DNA gels in acetone/water mixtures as well as in aqueous salt solutions is very similar to that of synthetic polyelectrolyte hydrogels. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013