Aspergillus niger is worldwide in distribution and has been isolated from numerous habitats. Humans are continually exposed to A. niger spores and vegetative forms on foodstuffs and in the air. The vast majority of strains of A. niger, especially those used in industrial fermentation, have a history of safe use. While there are sporadic reports to the contrary, most isolates have not been documented to be serious pathogens of humans, animals or plants. Specific strains may produce certain mycotoxins or may elicit allergic responses among workers. Those limited instances of adverse effects seem to be associated with a limited number of strains. With proper characterization of industrial strains, use of those with potential for such effects can be avoided.