The toxic hazards of exposure to 4-dimethylaminoazobenzene (60117) (DAB) are discussed. Numerous published research studies on the carcinogenicity of DAB in laboratory animals are summarized. Hepatoma incidence is described in rats fed diets containing various amounts of DAB, protein, and fat. The histologic progression of hepatomas in rats fed DAB is reviewed, including stroma proliferation, hyperplasia, and thickening of the argyrophil reticulin fibrils and mucopolysaccharides. The vascular pattern and microscopic structure of DAB induced liver tumors also are described. Other studies are cited which investigated the relationship between DAB chemical structure and carcinogenicity, and DAB binding to structures or fractions in biological material. Synergistic and antagonistic effects on DAB carcinogenicity are reviewed for nitrosamines, 20-methylcholanthrene (56495), 4- dimethylaminostilbene (1145739), carbon-tetrachloride (56235), trypan-blue (72571), and several other compounds. DAB induced skin tumors in rats are also noted, along with other studies of DAB carcinogenicity in dogs, rainbow trout, and neonatal mice. The author concludes that DAB has been shown to be carcinogenic in rats, mice, dogs, and trout and should be considered as a potential carcinogen to humans.