The effects of Reactive Red on the chromosome of Allium cepa are reported. A significant reduction in mitotic index was observed as the dose and time interval is increased as compared to control. The dye also induces different types of aberrations viz: anaphase with bridge, multipolar anaphase, metaphase with loss and stickiness. The dye at the highest concentration (1000 μg/L) induces highest number of chromosomal aberrations at different time exposure. Thus the results depict that under the dye at the evaluated doses and exposure times were mito-depressive and clastogenic. Cytotoxicity studies should be conducted for further evaluation of the effect of the dye in a natural system.