Agaritine is a naturally occurring phenylhydrazine derivative present in wild and cultivated Agaricus mushroom species, including the cultivated mushroom Agaricus bisporus. Agaritine has been described in some studies as a potential carcinogen, however, the scientific validity of the experimental designs and models from which this conclusion has been drawn have been contradicted and challenged by other studies. Feeding studies using mushrooms and mushroom extracts have in general provided no evidence of toxicological effects of agaritine or mushroom consumption, in contrast to results of studies which have administered non-physiologically relevant concentrations of chemically synthesized hydrazine derivatives to mice. The available evidence to date suggests that agaritine from consumption of cultivated A. bisporus mushrooms poses no known toxicological risk to healthy humans.