A toxic pyrrolidine alkaloid, irniine 111, was isolated from Arirarurn mlgare tubers, and its structure was elucidated by 2D COSY spectroscopic methods. Arisamm wlgareTarg.-Tozz. (Araceae), is widespread in Morocco and is named "irni"; the starch-containing tubers were, in the past, eaten by people during periods of scarcity. The consumption of large amounts induced several toxicologic manifestations, such as irritation of the mucous membranes, gastro-enteritis, and allergic symptoms, mainly dermatitis and pruritis, and sometimes led to death (1,2). Previous investigations on this plant report the presence of lipids, proteins, and non-specified alkaloids (2,3). We investigated the toxic components in the tubers of A. vulgare by using a bioassay employing the larvae of brine shrimp Artemia salina (4). The alkaloid fraction of the MeOH extract of the tubers demonstrated toxicity in this bioassay. We report here the isolation and structure elucidation of the main alkaloidal, toxic, component which is new and which is named irniine.