Two field experiments were carried out at a private farm at Sakkara, EL-Badrasheen, Giza, Governorate, Egypt, during two successive Summer seasons of 2004—2005 to study the Influence of cyanobacteria inoculation in different rates (0, 50 and 100% of the recommended dose, i.e.. 3.5 kg dried cyanobacteria inoculum fed“) individually or in presence and} or absence of different nitrogen levels (0, 25, 50 and 100% of the recommended dose. [i.e.),100 kg N fed") on maize yield and yield components. some maize grain technol09y characters (protein, oil. carbohydrates and ash percentages) as well as the biological activity of the soil remained after maize harvesting as represented by total count bacteria. cyanobacteria count. CO; evolution, dehydrogenase (DHA) and nitrogenase (Nz-ase) activities Results revealed that all tested treatments increased significantly both maize yield and its components over the control treatment. The highest yield components values were due to 100% N + 100% cyanobacteria and they were comparable to those recorded in presence of 50% N +100% cyanobacteria treatment. Also the values of maize yield components obtained due to 100% N treatment were not significantly different 1'ron'i those attained due to 100% N + 100% cyanobacteria and 50% N + 100% cyanobacteria treatments. Cyanobacteria inoculation at the rate of 50% combined with 100% N recorded the highest maize protein and carbohydrate percentages. Indefinite trend was noticed of maize oil % in response to cyanobacteria inoculation despite the highest insignificant oil % increments were noticed due to 50% N + 100% cyanobacteria treatment Also, Indefinite response was observed for ash % due to cyanobacteria inoculation. For soil biological activity, cyanobacteria inoculation enhanced significantly any of total count bacteria, cyanobacteria count, CO; evolution, dehydrogenase and nitrogenase activities compared to the control treatment received no inoculation. In conclusion, the use of cyanobacteria inoculation technology in cereal crop production such as maize may lead to reduce the amount of mineral nitrogen required for maize production by 50% as well as it ensures good yield quality and safe the environment contaminations resulted from the extensive use of the costly and hazard the so called mineral nitrogen fertilizer.