Abstract: The genotoxic effects of aqueous extracts of neem Azadirachta indica A. Juss., Meliaceae leaves, kernels and seed coats was evaluated using Allium cepa chromosome aberration assay according to the standard protocol of the plant assays established by The International Program on Chemical Safety and The World Health Organization. Neem extracts suppressed the mitotic activity of Allium root meristems after 24 and 48 h treatment with all concentrations. Neem seed coat extract was the least effective in its ability to inhibit cell division, whereas kernel extract was the most effective. Analysis of the data of phase index indicate that all treatments reduced prophase percentage, mean while the percentage of metaphases and ana-telophases rose over those of control. Also, the extracts caused different kinds of chromosome aberrations in dividing and non dividing cells of Allium cepa such as micronucleus and multinucleated cells observed in the interphase stage; bridges, stickiness, non-congression metaphase, laggards, polyploidy and disturbed ana-telophase observed in dividing cells. Bridges was the most frequent kind of aberration in dividing cells. Neem seed kernel extract proved to be induce more chromosomal aberrations than neem leaf extract and neem seed coat extract. Accordingly, neem extracts should not be used for internal medicinal purpose until more thoroughly tested, calls for a closer look at the genetic toxicological effects in different test systems for human welfare.