Vinyl acetate monomer (VAM) was administered in drinking water at doses of 5,000, 1,000, and 0 ppm (v/v), to Swiss mice, 17 weeks old (breeders) or 12-day embryos (offspring) at the start of the experiment. The treatment lasted 78 weeks, and the animals were kept under control until spontaneous death. VAM has been shown to cause an increase in: (1) total malignant tumors; (2) carcinomas of the Zymbal glands, oral cavity, tongue, esophagus, and forestomach; (3) stomach tumors; (4) lung tumors; and (5) uterine tumors. A slight increase of hepatomas has been observed among male mice offspring treated with the higher dose. On the basis of these data VAM must be considered a multipotential carcinogen.