An experiment aimed to examine the effect of aqueous extracts of three weed species on soybean roottip- cell mitosis has been carried out at the Laboratory of Plant Physiology and Biotechnology. Department of Agronomy and Soil Science, University of New England, Australia. Aqueous extracts of fresh weed material ('Amaranthus Cyperus rotundus' and 'Paspalum dilatation') at the concentration of 25% ( w/v) were added to the germination medium of soybean seeds cultivar Banjalong, Melrose, and Valiant. The germination was conducted at a growth cabinet with 25°C and total darkness. All experimental units were arranged in a completely randomized design with 5 replication. Radicles (roots) from the germinating soybeans were harvested when they were about 1 – 1.5 cm long. The soybean root tips were used to observe the mitotic index following a series of hydrolysis and staining process. Results indicate that aqueous extracts of the weeds reduced cell division of the soybean regardless of the cultivars. This contributes to the understanding of the modes of action of the allelopathic effect of the weeds. 'Amaranthus powellii' had the most inhibitory effect to the soybean cell division.