The following fungal metabolites represent a wide diversity in chemical structure and, therefore, cannot be grouped according to chemical similarity. Therefore, they have been placed into four groups, three of which are based on the genus most likely to produce them and one miscellaneous group. These groups are Aspergillus toxins, Penicillium toxins, Fusarium toxins, and miscellaneous toxins. As might be expected, they also produce a wide variety of biological effects. In some cases, only acute toxicity was observed (i.e., aspergillic acid, oosporein, and moniliformin). Many, such as citrinin, possess antibiotic properties in addition to effects on animals and/or higher plants. Slaframine, butenolide, and zearalenone have been implicated strongly in the etiology of naturally occurring toxicoses, whereas others (such as cyclopenin and viridicatin) apparently show little or no acute toxicity to animals. Their chemical size and complexity vary from that of moniliformin, a C 4 cyclobutene-type compound, to that of roseotoxin B, a complex cyclic peptide.