Mycorrhizal fungi increase soil nutrient and water absorption as plant symbionts. Root nodule bacteria, beside fixing atmospheric nitrogen, have the ability to produce antibiotics and phytoalexins, etc. The use of these two symbionts together appears to be more beneficial for plant growth than their use individually. The results of most studies indicate that mycorrhizal fungi and root-nodule bacteria generally reduce the severity of nematode diseases of various crops. There are possibilities for biological control of nematodes by selecting effective strains of mycorrhizal fungi and root-nodule bacteria, despite some obstacles.