Abstract: A case of intoxication in Sweden caused by Gyromitra ambigua (Karst.) Harmaja (Ascomycetes: Pezizales), a species previously not known to be poisonous, is reported. The fresh fruit bodies were boiled but the boiling water was taken with the dish and eaten, too. Three other cases of poisoning, occurred in Alaska and Finland and caused by fruit bodies of G. infula (Fr.) Quél. coll. (i.e., either G. ambigua or G. infula) which were fresh prepared for dish without boiling and rinsing, are also discussed. On the other hand, two different cases are known when fruit bodies of G. ambigua kept in boiling water (the water not being used for the dish) did not cause any effects of intoxication. Dried or boiled and rinsed fruit bodies of G. infula coll. apparently have never been reported to have caused poisonings. The symptoms of the present cases are very similar to those known to occur in intoxications caused by the famous relative species, G. esculenta (Pers.) Fr. These facts suggest that the toxically effective substance of G. ambigua is the same as (or chemically closely related to) that in G. esculenta, i.e. gyromitrine. G. infula s. str. is apparently intoxical.