Sanguinarine (SG), a benzophenanthridine alkaloid, has been shown to possess anti-microbial, anti-inflammatory and antioxidant properties. In the UK and USA its salts has been in use in mouthwashes and toothpastes to inhibit dental plaque and improve gingival health. In India and Nepal consumption of mustard oil contaminated with argemone seeds containing sanguinarine, was associated with "dropsy" syndrome. In the present study, SG was evaluated in vivo in mouse bone marrow cells for its ability to induce clastogenicity and DNA damage in terms of increased sister chromatid exchange (SCE) frequencies. Doses of 5, 10, and 15 mg/kg body weight of SG given intra peritoneally induced a positive dose-dependent significant clastogenicity and SCE frequency increases (trend test alpha < or = 0.05). The minimum effective concentration to induce clastogenic and DNA damage was 10mg of SG/kg body weight. In addition to examining SCEs, the BrdUrd-differential technique was utilized to assess the effect of SG on cell replication. The analysis revealed that SG treatment did not significantly affect the distribution of cells among the different phases of the cell cycle. The proliferation rate index and average generation time data were statistically non-significant. This indicated that the alkaloid was not cytotoxic to the bone marrow cells at the doses tested. Based on the results of the present findings, the use of this alkaloid should be restricted.