Malachite green (MG) consisting of green crystals with a metallic lustre, is very soluble in water and is highly cytotoxic to mammalian cells and also acts as a liver tumor promoter. In view of its industrial importance and possible exposure to human beings, MG poses a potential environmental health hazard. The malignant transformation of Syrian hamster embryo (SHE) cells by MG has been reported earlier. In this study, an attempt has been made to study the levels of vimentin, vimentin phosphorylation and the expression of PCNA and BrdU incorporation in MG transformed cells compared to control cells. Immunohistochemical and immunoprecipitation studies showed enhanced levels of vimentin in transformed cells compared to normal cells. Metabolic labelling studies showed an overall increase in phosphorylation of total cellular proteins as well as hyperphosphorylation of vimentin in transformed cells. Transformed cells also showed an increased doubling time, PCNA expression and BrdU incorporation. This study indicates a close relationship between vimentin levels, hyperphosphorylation of vimentin and increased cell proliferation associated with the malignant transformation of SHE cells.