Summary Peganum harmala extract caused an increase in mitotic index of Zea mays treated cells with increasing the time of treatment in all cases. Depression of cell division in these cells increase with increasing the concentration of the extract in almost all treatments, however, roots treated with the highest concentration showed decreased in their mitotic index. Harmala extract at 100% concentration induced a variety of cytogenetic variants of which ten classes were observed. These include abnormalities in chromosomal organization (distinct chromatid separation, visible chromatids, despiralization, C-bands, ring chromosomes) and nuclear organization (laggard chromosomes, anaphases with bridges, micro and multi nuclei, C-metaphase, polar metaphase). The frequency of abnormalities are significantly higher than controls in all treatments studied. These results suggest that harmala can act at many levels of organization and cause a wide range of abnormalities involving all the stages of mitosis in Zea mays root tips.