Abstract: In contribution to a more sustainable agriculture, a comparison was carried out between two plant growth promoting rhizobacteria, namely Paenibacillus polymyxa (PP) and Bacillus megaterium var. phosphaticum (BM) as phosphate dissolvers, in presence of rock phosphate. Biofertilizer treatments were applied individually to tomato plants (Lycopersicon esculentum L.) cv. Super Strain B during 2008 and 2009 spring seasons. Effects of rock phosphate and phosphate solubilizing microorganisms on some microbial activities, vegetative characteristics as well as fruit yield and quality of tomato were studied and compared with uninoculated treatment fertilized with mineral phosphate fertilizer (calcium super phosphate) as control. Significant positive effects were obtained with microbial activities (dehydrogenase and phosphatase) vegetative characteristics, photosynthetic pigments, mineral contents (N, P, K and Mg), total sugars, total carbohydrates and crude protein in leaves as well as fruit set, early, total yields and quality (T.S.S., Vit. C and acidity) of tomato in response to addition of rock phosphate with phosphate solubilizing microorganisms when compared with uninoculated treatments. The highest records of all tested parameters were recorded with rock phosphate inoculated with Paenibacillus polymyxa plus Bacillus megaterium treatment. This work shows that by inoculating phosphate solubilizing microorganisms with rock phosphate under field conditions in Egypt it is possible to obtain tomato yields comparable to those produced by using the expensive calcium super phosphate fertilizer. Key words: Tomato, Lycopersicon esculentum, rock phosphate, phosphate solubilizing microorganisms,fruit yield.