Abstract: Allelopathic effect of leaf extracts (different concentration) of Acacia auriculiformis and its possible phytotoxicity was tested in a laboratory experiment by using some agricultural crops e.g. Brassica juncea (L.) Czern & Coss; Phaseolus mungo L.; Raphanus sativus L. and Vigna unguiculata (L.) Walp. and Cicer arietinum L. as a bioassay material. The experiment was conducted in sterilized petri dishes with a photoperiod of 24 hours on an average of 29°C. The effects of the different concentrations of aqueous extracts were compared to distill water (control.). The aqueous extracts caused significant inhibitory effect on germination, root and shoot elongation and development of lateral roots of receptor plants. Bioassays indicated that the inhibitory effect was proportional to the concentrations of the extracts and higher concentration (50-100%) had the stronger inhibitory effect whereas in some cases the lower concentration (10-25%) showed stimulatory effect. The study also revealed that inhibitory effect was much pronounced in root and lateral root development rather than germination and shoot growth.