There has been considerable interest and concern in recent years regarding the potential health effects of mycotoxins in the indoor environment. Although the existence of mycotoxins has been known for several decades, relatively little is known about their effects in humans. What is known comes almost exclusively from studies of ingestion as the route of exposure. This review summarizes what is known regarding health effects of mycotoxins in general and specifically examines the evidence for the role of indoor exposure to the fungi of the genusStachybotrysas a cause of disease in humans. Much work remains to be done in the area of mycotoxin research. The risk of health effects from ingestion seems much more widespread than from indoor airborne exposure, although the latter has received considerably more media attention. Rigorously controlled studies are needed to clarify these issues.