Mycotoxins are fungal secondary metabolites that sometimes contaminate agrifoods such as corn, wheat and peanuts prior to harvest and during storage. Because of their capacity to affect human and animal health, two key areas of mycotoxin research have been analysis and toxicity assessment. Research initiated in the late 1970s proposed the application of immunochemical assay to the analysis of aflatoxin B1(AFB1) and other mycotoxins. The most common assay, ELISA, involves the competition between a free mycotoxin in a sample extract with an enzyme‐labeled mycotoxin for an antibody binding site. This and other assays have been made available commercially for the rapid assay of mycotoxins in food. Important points to consider relative to development and application of mycotoxin im‐munoassays are: method of antibody production, adaptability to food analysis and multi‐analyte methods. In recent years, there has been increasing evidence that mycotoxins alter the intricate balance of the immune system. In experimental animals, vomitoxin and potentially other trichothecenes impair normal immune function and induce an autoimmune disease, IgA nephropathy. Trichothecene‐mediated immune suppression is readily explainable by its potent capacity to inhibit protein synthesis. Its ability to stimulate certain immune functions such as IgA hyper‐production IgA might be explained by superinduction of T‐cell cytokines.