The cytological effects of many herbicides have been studied on different plant materials e.g. Ioxynil on roots of Vicia faba and Pisum sativum (Rost et al. 1977), Fluometuron on roots of wheat and broad bean (El-Sadek and Ashour 1978), Stomp on roots of Allium cepa (Mousa 1982), Glean on roots of Allium cepa and Vicia faba (Badr and Ibrahim 1987), Igran and Garlon-4 on roots of Allium cepa (El-Khodary et al. 1987, 1989). It has been found that all of these herbicides were antimitotic and caused various types of mitotic aberrations such as C-metaphase, polyploid cells, multipolars, bridges and laggards. The use of chromosomal aberrations, induced by pesticides in crop plants, is therefore being accepted as indicators of genetic damage (Ma 1982). Tribunil (N-2-benzothiazolyl-N, N-dimethylurea) is a broad spectrum herbicide. It is also known as methabenzothiazuron.