Brick cheese was placed in plastic containers and all surfaces except the top were sealed with wax. The top was inoculated with Aspergillus flavus or Aspergillus parasiticus and cheese was incubated in a humid chamber at 7.2, 12.8, and 23.9 C for up to 14 weeks after mold growth was evident. After incubation each cheese was cut horizontally into four layers, each approximately 1 cm thick. Each layer of cheese was extracted with a monophasic-biphasic solvent system (chloroform, methanol, and water). The extract was purified, concentrated, and aflatoxins were measured by thin-layer chromatography and fluorometry. No aflatoxins were produced by either mold at 7.2 C. At 12.8 C, A. parastticus developed aflatoxins B1 and G1 after 1 week of incubation. Aflatoxin produced by this mold persisted through 4 weeks of storage and then was not detectable. Aspergillus flavus did not form aflatoxin at 12.8 C. Both molds produced aflatoxin on cheese at 23.9 C; A. parasiticus did so after 1 week and A. flavus after 14 weeks. In some instances, aflatoxin was found in cheese 4 cm from the surface. It is reasonable to assume that cheese will not become contaminated with aflatoxin if the food is held at or below 7 C.