Mycotoxins are chemical compounds, produced by a variety of fungi, that can cause illness in humans and animals. This paper is a review of literature on mycotoxins with emphasis on mycotoxins in indoor air. Consideration is given to specific mycotoxins identified in indoor air, indoor sources of the mycotoxins, factors affecting mycotoxin production, potential health effects indicated by animal laboratory studies, and case studies of possible human inhalation health effects of these mycotoxins. Historically, mycotoxicoses have been associated with consumption of moldy grain. In recent years, some attention has been given to mycotoxins in dust from agricultural environments, but relatively few studies have examined mycotoxins or mycotoxin‐producing molds in indoor environments. The few indoor studies suggest that mycotoxicoses may occur in some indoor environments. More studies are needed to understand the potential for mycotoxin occurrence and significance in indoor environments.