Nitrogen, is a vital element for the plant growth, even though it is found in abundance in the atmosphere (78%) it remains a limiting factor for the agricultural production and to use of chemical fertilizers with nitrogen represent a major costing element for the crops. In order to reduce the quantities of nitrogen based chemical fertilizers as well as the environmental pollution the attention turned to the processes of atmospheric nitrogen fixation which has a great importance and is a viable alternative to supply the vegetables with this important element and which will have later a benefic effects on the following cultures. Among the alternative solutions to the chemical fertilizers in agriculture one can find the bio-fertilizers, products based on the capacity of the soil bacteria to fixate, by means of symbiosis, by association or freely, the nitrogen from the atmosphere and to feed it to the plants in an accessible form, together with other bioactive substances such as bio-hormones. In order to study the process of biological fixation of the atmospheric nitrogen by means of bio-fertilizer Biotrofin and under the influence of microelement molybdenum in Arad agro ecological area (1997-2000), area characteristic for the western side of the country, were carried out a range of researches on the sowing garden bean cultures. The bacterial product used to treat the bean seeds was Biotrofin (10 l/ha), product that has two living components: a nitrogen fixating bacteria, that gets its nitrogen from the atmosphere and a second bacteria, Bacillus megaterium, that dissolves the tricalcium phosphate rendering it accessible to the plants. Microelement molybdenum was used by means of seed dusting (210 g sodium molybdate for the quantity used to sow a hectare) and by culture sprinkling with 900 l solution/ha, the solution having 210 g ammonium molybdate, during various stages of plant developing: at 15 cm height, at flowering, at pods formation and at beans formation. The results obtained during the experimentation period show high yields increases for the variants treated with Biotrofin and under the influence of microelement molybdenum provided at pods forming stage. The average of the morphological indexes of the plants reflect the results of the seed yield per hectare.