A cell line designated as MA782/5S-8102 has been established from mouse mammary carcinoma model （MA782/5S）by monolayer culture, It has been cultured for about 3 years since it was grown in vitro. The growth medium was RPMI-1640 supplemented with 20% newborn calf serum, insulin （0.23u/ml）, penicillin （100u/ml） and streptomycin （100 μg/ml）. The morphology of MA782 /5S-8102 cells was described. It was not identical in size and shape of the cells. The epithelioid cells were predominated, a small number of cells were round and oval, and the giant cells occasionally appeared. The great majority of cells were with one nucleus, the minority were with 2 nuclei, and individual giant cells multinucleated （≥ 3 nuclei/cell）. An inoculum of 3×10,4, cells/ml multiplied ,approximately 31.77 fold in 5 days. The mitotic index as determined by counting 2.200 cells daily in 6 days showed an increase to as much as 60.5‰ on the 2th day and then gradually decreased to 7.2‰ on the 6 th day. Chromosome analysis based on observations of 250 metaphase"chromosomes showed a wide variation of chromosome number （31-267） with a mode around 85-95 （50.4% frequency）. Many types of marker chromosomes were found in this cell line. Four types of marker chromosomes were frequently observed, i.e. metacentric, teloceatric with the secondary constriction, minute and double minute chromosomes. The phenomenon of cell agglutination was observed obviously in the cells of this cell line treatmented with ConA （50μg/ml）. When the cell suspension of MA782/5S-8102 cells prepared in two different concentrations were respectively transplanted into the normal 615, SW/G and hybrid mice, 100% of the mice injected ,developed a solid tumor with structure and cellular morphology similar to those of the original MA782/5S solid tumor.