<jats:p>We isolated four Pyrrolizidine Alkaloids (PA) from Senecio nemorensis L. growing in Mongolia. Their structures were elucidated by spectroscopic methods to be 7-Senecioyl-9-sarracinoyl-retronecine, Retroisosenine, Doriasenine and Bulgarsenine. The alkaloidal pattern is very similar to that of the European Senecio nemorensis L., ssp. nemorensis (Rchb.) Celak. The medicinal use of this plant or of preparations from it may be hazardous to human health because of the high PA level in the plant (≈ 0.1%) and the fact that three of the PA are known to have toxic side-effects.