The effect of citrus pectin (CP) on the proliferative capacity of four malignant cell lines was examined. Various dose of CP inhibited the proliferation of two-colon carcinoma and an erythroleukemia cell lines. Raji cells were not affected at all. The three lines affected by CP are known to express galectins which are pivotal for cell growth and metastasis, while Raji cells, whose proliferation was not affected by CP, are deficient of this betagalactoside. It is possible that the antiproliferative effect of CP on the malignant cells may be due at least in part to its ability to inhibit galectin expression.