Since April 1984, we have transplanted 10 human adenocarcinomas to BALB/c nude mice and subcutaneous growth was obtained with 5 tumors. Two tumors were lost during 1st passage and 2nd passage due to accidental death of tumor bearing nude mice. Now SCN-1, SCN-2 and SCN-4 human colon adenocarcinomas are serially Passed for 5, 10 and 6 gene- rations. The histologic findings of both original human tumor and those of nude mice were compared. The subpassage tumors resembled those af original ones in terms of differentiation. However, emergence of calcification, extensive necrosis and scanty stroma were distin- guishing features. Although degree of mucin production waa unpredictable during the passages, one colon cancer classified as signet ring cell carcinoma was suceessfully trans- planted and grafted tumor exhibited exactly same histologic feature.