The fine structure of HeLa cells treated with several mycotoxin-producing fungi (Aspergillus flavus ATCC 15517, Aspergillus parastiticus RIB 1037, Penicillium toxicarium RIB 4002, Penicillium cirinum SWU)238, Penicillium islandicum IFO 5235, Penicillium tadum IFO 5787 and Pencillium brunneum RIB 1172) has been examined and some details have been descried. The normal HeLa cell have numerous microvilli, large ovoid nucleus, pleomorphic mitochondria, electron-dense body, Golgi complex, mid-body and endoplasmic reticulum etc. Certain specific structural changes induced by culture filtrates of several mycotoxin-producing fungi have been noted. These alterations induced disappearance of Golgi complex, rER vacuolization, nucleolus attachment to the nuclear envelope nad appearance of certain vacuoles. There were not any changes by the treatment of culture filtrates of non-toxic fungi and only cell debris of some specimens can be observed by the injury of culture filtrates. The experimental animals treated with mycotoxin-producing fungi (Aspergillus flavus ATCC 15517, Aspergillus parasilicus RIB 1037, Penicillum citrinum SWU 238, Penicillium toxicarium RIB 4002, and Penicillium islandicum IFO 5235) were mal cells treated with culture filtrates.