To investigate the pathological differences between spontaneously developed and chemically induced liver cancers in LEC rats with hereditary hepatitis, eight-week-old LEC rats were fed 0.06% or 0.03% of 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) for 12 weeks, and then fed basal diet. Spontaneous liver cancers occurred in 60.4% of the LEC rats, while 3'-Me-DAB induced cancers in all LEC rats. The survival periods of chemically (0.06%) treated LEC rats were significantly shorter than non-treated rats. The chemically-induced cancers were strongly related to Edmondson classification. Metastasis and transplantability of the chemically-induced cancers were higher than spontaneous cancers. LEC rats are highly susceptible to the chemical carcinogen with the initiated status of hepatocarcinogenesis.