Two new 13-membered macrocyclic pyrrolizidine alkaloids, (13R)-13- hydroxyretroisosenine (2b) and (12S)-12-hydroxyretroisosenine (2c), have been isolated from Senecio roseus and Senecio helodes. Their Structures were established from spectral and chemical studies including 2D NMR. The hydrochloride of retroisosenine (2a · HCl) was also isolated, and its absolute configuration was determined by X-ray diffraction analysis.