The inoculation of P-solubilizing microorganisms is a promising technique because it can increase P availability in soils fertilized with rock phosphates. Several authors have identified the ability of fungi, mainly of Aspergillus & Penicillium genus, to solubilize phosphates under in vitro conditions. That ability is generally associated to the release of organic acids, decreasing the pH. Moreover, these organic acids can increase considerably P in the soil solution through the quelation of Ca, Fe and Al, change reactions & solubilization of low soluble salts. Beyond the phosphate solubilization, many P-solubilizing microorganisms increase the mycorrhizal root colonization by production of specific metabolites as vitamins, amino acids & hormones. Therefore, there is a demand on studies on this subject, in order to improve the functional knowledge of compatibility of those microorganisms aiming at their coinoculation to increase the nutrition and growth of plant species.