Weed affects groundnut through direct competition for light, nutrient and moisture as well as through allelopathy. The allelopathy is related to the production and release of some beneficial or harmful chemicals into the environment by one plant on another. The existence of allelopathic effect of weeds in oilseeds and legumes have been reported by various workers. But the magnitude of effects varies with the weed species. Aqueous extracts of Lantana camera, Digera muricata, Chenopodium album, Ageratum conyzoides, Ciscium arvense, Abutilon indicum and Cyperus rotundus caused significant reduction in germination of seeds, shoot and root length of groundnut. However, root, shoot or whole plant extract of Amaranthus spp. increased the germination and seedling vigour of groundnut as well as growth of Rhizobium spp.