Allelopathic effect of Cyperus rotundus, Commelina benghalensis, Parthenium hysterophorus and Prosopis juliflora at two concentrations (5 and 10 % W/V ) on sorghum, wheat, green gram, soybean,  and  sunflower and groundnut was studied.  The results revealed that Commelina and Cyperus extracts had greater inhibitory effect on germination, seedling length and seedling vigour index, among the crops tested. Groundnut and wheat were more resistant to allelopathic effect to weeds.