The Pyrrolizidine Alkaloids (PAs) are a group of chemicals found in a variety of plant species throughout the world. These toxic alkaloids are distributed mainly in Senecio (Compositae), Crotalaria (Legominosae) and Heliotropium (Boraginaceae) species. Plants containing these alkaloids cause significant mammalian morbidity and mortality, especially in humans. Upon ingestion, metabolic activation in liver converts the potent compounds into highly reactive electrophiles capable of reacting with cellular macromolecules forming adducts, which can initiate acute or chronic toxicity. One of these plants is Senecio vulgaris which is abundant in wheat farms of Mazandaran province. When wheat (Triticum spp) is being harvested, seeds and aerial parts of Senecio would also be collected with it. Since the presence of PAs in Senecio vulgaris is proven in a previous research, hence in this study, quality andquantity of PAs of wheat and flour contaminated with Senecio in Mazandaran province farms have been studied. The specimens were collected from all flour industries four teen sites and silo of Mazandaran. The Ehrlich reaction test and spectrophotometeric method were used for the qualitative and quanlitative examinations,respectively. The Amount of PAs and their N-oxides calculated on the basis of senecionine. The reaction is specific for alkaloids having an unsaturated basic moiety of D3– pyrroline ring. In the qualitative test, the existence of PAs was demonstrated in all specimens. Mean amount of the total PAs and their N-oxides in 0.512g of specimens was 0.020 to 0.05 mg (as senecionine). Total PAs in 0.512g of Senecio vulgaris was 0.4mg. LD50 of senecionine, fatal toxic dose of PAs and nonfatal toxic dose of PAs are 64.72 ± 2.24 mg/kg, 6–167 mg/kg, and 2–27 mg/kg, respectively. Comparing the amount of PAs in wheat and its flour as well as its toxic dose, the specimens would not scem to produce acute complications of Pas. However, long term exposure to low levels of PAs may cause cumulative damage especially hepatotoxicity. Meanwhile chronic toxicity to humans by diet, including the specimens, is possible.