The purpose of this study was to identify specific chromosomal abnormalities that might be involved in colon cancer metastasis. For this reason, we performed extensive karyotypic analysis on two colon cancer cell lines (SW480 and SW620) established from two surgical biopsies taken at different intervals and representing different stages of the disease from the same patient. Despite the karyotypic heterogeneity, several marker chromosomes were shared between the two cell lines, indicating their common origin. We hypothesized that these shared chromosomal aberrations might be critical for the continuous growth of the tumor cells and, therefore, were retained through progression of the disease. Duplication of 16q and new or additional structural chromosomal abnormalities involving breakpoints 3p21, 8p11, 10q25, 13q14, 14q11 and 15q15 were observed as the characteristic anomalies only in the SW620 cell line. As SW620 was established from the abdominal metastatic lesion of the patient, we postulated that the acquisition of these new markers in the progression steps of the primary tumor might represent "hot-spots" that possibly contain genes crucial for metastatic potential in colon cancer.