This study was carried out at the experimental nursery of Horticultural Research Institute; AgriculturalResearchCenter, Giza, during the two successive seasons of 2005 and 2006. The main objective was to study thepossibility of using biofertilization (Rhizobacterein and Phosphorein) to reduce the need for mineral fertilizers and study its effect on the vegetative growth, flowering and chemical composition of Helianthus annuus L. (Big Smile) plants.   The results indicated that using a combination of Rhizobacterein and Phosphorein promoted plant height, leaf area and total carbohydrates, compared to using each biofertilizers alone or in combination with half the full rate of chemical fertilization (full rate= 10 g Christalon/plant). Using half the amount of chemical fertilizers and replacing the other half by the combination of biofertilizers caused an increase in number of leaves, fresh and dry weights, and the leaves contained much more total chlorophylls and potassium. This treatment also caused a significant increase in number of lateral flowers. It could be concluded that treating sunflower (Big Smile) plants with 5 g Rhizobacterein and 10 g Phosphorein plus 5 g Christalon per plant produced the most vigorous vegetative growth and the largest number of lateral flowers with good characteristics.