A formaldehyde-free adhesive consisting of soy flour, polyethylenimine, maleic anhydride, and sodium hydroxide was investigated for making randomly oriented strandboard (R-OSB) and oriented strandboard (OSB). The hot-press conditions and the adhesive usage rate were optimized in terms of enhancing internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity (MOE) of the resulting R-OSB and OSB. The IB, MOR, and MOE were the highest at a hot-press temperature of 170 degrees C, a hot-press time of 4-5 min, and an adhesive usage rate of 7%. The strengths of the OSB panels made with this formaldehyde-free adhesive were compared with those of commercial OSB panels purchased at a local Home Depot store.