Four Senecio species were analyzed by gc-ms for their pyrrolizidine alkaloid content. This is the first published report of pyrrolizidine alkaloids in Senecio serra, Senecio dimorphophyllus, and Senecio hydrophyllus. Previously undetermined pyrrolizidine alkaloids from Senecio mikanioides were also tentatively identified. Gc-ms analyses showed the presence of the stereoisomers senecionine [9] and integerrimine [11] in S. dimorphophyllus and complex mixtures of monoester and diester pyrrolizidine alkaloids in the other three species. Tentative structural identifications were made of ten new pyrrolizidine alkaloids. These new alkaloids are isomers of triangularine, sarracine [13], 7-angelylplatynecine [5], 7-angelylretronecine [2a], and acetylated macronecine-type alkaloids. All three species contained both saturated and unsaturated pyrrolizidine alkaloids, and all had at least ten individual alkaloids. The mass spectral features and gc elution order of these compounds are discussed and the pyrrolizidine alkaloid profiles of the plants are compared. The potential toxicity of the three species to range animals is discussed.