The toxic effects of beta-propiolactone (57578) (BPL) are reviewed. The physical properties of BPL, its solubility in water, and its method of production are described. The use of BPL as an intermediate in the manufacture of acrylates is noted. The reactivity of BPL with nucleophilic reagents is reviewed, and its ability to bind to DNA is discussed. BPL induction of skin irritation and blisters in humans is noted, along with its irritant effects on the eyes, nose, throat, respiratory tract, and other mucous membranes. BPL mutagenicity in root tips and bacterial cultures is described. The results of a variety of BPL carcinogenicity tests are summarized, including studies with rats, mice, and guinea-pigs exposed to BPL by subcutaneous injection, dermal treatment, intravenous injection, tracheal application, intragastric administration, intraperitoneal injection, and ingestion. The tumor initiating potential of BPL is also discussed. The in-vitro effect of BPL on rat fibroblast cells is described, including cell death and cytoplasmic damage. The author concludes that BPL has been established as a carcinogen in laboratory animals, and is probably a human carcinogen.