Thirty samples each of wheat and rice and 22 of maize were screened qualitatively and quantitatively for the presence of mycotoxins out of which 13, 15 and 7 samples respectively were found to be contaminated with different mycotoxins. Aflatoxin was present in 37.4% samples and besides aflatoxin, ochratoxin A, sterigmatocystin, citrinin, rubratoxin and zearalenone were also present in the cereals. The quantity of aflatoxin was highest in rice samples in comparison to wheat and maize. During the preliminary bioassay no external changes were observed in the mice except for slight weight loss when fed with grain samples, while a high rate of mortality was observed when treated with lethal doses of mycotoxins.