A study has been carried out to determine the levels of radioisotopes in five Canadian grains from pre-(1985) and post-Chernobyl (1986) crop years. In addition, the radioisotope levels were determined in grains from the 1988 crop year consisting of wheats, oats, barley, corn and oil seeds which included flax, sunflower and canola. The grain and oil-seed samples were ashed to reduce their volume, and the gammaemitters137Cs and40K were determined using a high-purity germanium detector and a high-purity germanium well detector. The90Sr activity measurements required further ashing of the samples followed by chemical separations and -counting of the separated daughter90Y. The results for the 1985, 1986 and 1988 crop years are discussed and compared with results from grain crops obtained during years of atmospheric bomb tests in the 1950's.