The effect of seed treatments of common bean plants (cv. Nebraska) with Bion, Salicylic Acid (SA) and Paenibacillus polymyxa on infection with Rhizoctonia solani under greenhouse and field conditions was investigated. In greenhouse experiment, all treatments decreased percentages of pre and post-emergence damping- off compared with control grown in infested soil by R. solani. The highest percentage of survival plants was achieved from treatment with Bion 5mM (80%) followed by each of Bion 3mM and SA 5mM (76.7%) compared with control (40.1%). Meantime, significant increases in the values of shoot length, shoot dry weight and root dry weight over the control treatment were achieved. Under field experiments during summer 2009 and 2010 growing seasons, all the tested treatments significantly increased the percentage of survived plants compared with the control. There were no significant differences between the treatments with Bion 3mM and fungicide (Rhizolex-T 3g/Kg seeds) 89.4% and 89.3 %, respectively compared with untreated control 67.9% calculated as means of the two seasons. Also, the treatments with salicylic acid and P. polymyxa were less effective regarding survival plants in 2009 and 2010 growing seasons. Moreover, all treatments significantly increased all the studied vegetative characteristics, i.e. stem length, number of leaves/plant as well as fresh and dry weight of leaves/plant compared with untreated control. Meanwhile, higher increase pe in seed yield (kg/feddan) was estimated with bion and fungicide treatments (86% and 87.7%, respectively) followed by salicylic acid and P. polymyxa (66.8% and 55.4 %, respectively) increasing over the untreated control calculated as means of the two seasons. Laboratory studies indicated that, all treatments were effective in eliciting the activities of peroxidase and polyphenol oxidase. Peroxidase activity was higher with Bion followed by SA treatments; they showed 77.7% and 41.2 % increase over the untreated control, respectively. Meantime, elevation of the polyphenol oxidase activity was showed with Bion followed by SA treatments as 97.7% and 58.0% increasing over the untreated control, respectively. However, Bion treatment resulted in the highest increase in total phenols contents over the untreated control (94.3%) followed by SA and P. polymyxa treatments (57.9% and 52.6%) over the untreated control, respectively.