A sensitive and specific method for aconitine extraction from biological samples was developed. Aconitine, the main toxic alkaloid from plants belonging to Aconitum species (family Ranunculaceae), was determined in plant material by an external standard method, and by a standard addition calibration method in biological fluids. Described here is one fatal case and five intoxications of accidental aconitine poisoning following the ingestion of aconite mistaken for an edible grass, Aruncus dioicus (Walt.) Fernald, "mountain asparagus", and Cicerbita alpina (L.) Wallroth. The aconitine content in urine was in the range 2.94 microg/mL (dead patient)-0.20 microg/mL (surviving patients), which was almost two to four times higher than that in plasma.