Effect of bentonite and ash additives on the leaching and strength properties of cement-resin matrix was investigated. Three groups of samples have been prepared by cementation of low-level-radioactive resin. These are (A) cement-resin-ash matrix, (B) cement-resin-bentonite matrix and (C) cement-resin matrix. Each of the samples has different amounts of resin, cement, water and additives. Water/Cement ratio of the samples was arranged in the range of 0.4-0.5. Group (A) samples included fly ash as an additive in the range of 10-30% (w/w). Group (B) samples included bentonite as an additive in the range of 3-12% (w/w). Group (C) samples were prepared without any additives. Leaching rates of radionuclides (Co-60, Cs-137) and stabilities of these waste forms were compared to each other. Although long-term leach tests showed that bentonite additives significantly decrease the leaching rates (4.85 x 10(-8) kg m(2)/s for Co-60 and 2.68 x 10(-8) kg m(2)/s for Cs-137), compressive strength of these samples was not sufficient for handling. Optimum values have been measured by the tests of samples B4 and B5 in this group. Bentonite contents of these samples were between 5 and 7% (w/w). Evaluation of test results showed that optimum ratio of resin to matrix material was between 0.36 and 0.67. (c) 2006 Elsevier Ltd. All rights reserved.