The mutachromosomal and mutagenic effects of water soluble extracts of different forms of tobacco preparations used in India, were observed on the plant system Allium cepa in vivo. The four forms of tobacco tested prepared by different processing methods. Mitotic index indicated that certain concentrations of tobacco extracts were mitogenic in Allium cells. The abnormalities recorded were stickiness, somatic bridge formation, diplochromatid and clumping. The mode of processing did not appear to make any appreciable change in affecting cell and chromosome division. © 1992, Japan Mendel Society, International Society of Cytology. All rights reserved.