A field experiments were carried out at EL- Ismailia Agric. Res. Station (ARC), EL- Ismailia Governorate, Egypt, during the Summer seasons of 2007 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^-1) individually or in presence and/ or absence of different nitrogen levels (0, 50 and 100% of the recommended dose, (i.e.),100 kg N fed^-1) on maize yield and yield components and the biological activity of the soil  remained after maize harvesting as represented by total count bacteria, cyanobacteria count, CO₂ evolution, dehydrogenase (DHA) and nitrogenase (N₂-ase) activities. As well as, the soil native mycorrhiza were examined at two periods of 45 and 90 days from maize sowing n response to the tested treatments.    Results revealed that all tested treatments increased significantlyboth 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 werenotsignificantlydifferent from 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 inoculationdespite the highestinsignifecant 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, CO₂ 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.