Fungi and the mycotoxins that they produce are rarely the focus of a medical curriculum. One encounters historical references to ergots or aflatoxins, but the number of known fungal compounds with adverse effects on human health could be in the hundreds or thousands. The compounds contaminate grains, such as rice, wheat, rye, and maize, that are the staples of the human diet around the world. Different species of fungi can produce nearly identical toxins or a single species can produce a myriad of different compounds, complicating the task of linking exposure to effect. Chronic mycotoxin exposure burdens a significant percentage of the world population, with adverse effects on growth, fertility, and the incidence of cancer. Regulations in the United States attempt to protect consumers from high levels of exposure, but the individual medical practitioner is unable to test for these toxins in the routine care of patients. Some inflammatory respiratory conditions are also linked to mycotoxins and endotoxins, and these conditions can be prevalent in rural farming communities.