The symbiotic interaction of rhizobia with Legume roots results in nodule formation and eventually nitrogen fixation. An alternative to nitrogenous fertilizers is the application of rhizobia for common bean production, which convert atmospheric dinitrogen to reduced ammonium, suitable for plant use. Inoculant formulations must include local elite rhizobia because they can compete with the indigenous rhizobia in the soil and tolerate the harsh conditions found in many tropical soils. I describe the symbiotic interaction between rhizobial strains with common bean roots and the threat to which they are often exposed in harsh environments (low pH; high aluminum levels in soil, drought). Local rhizobial strains are often better adapted to their soil environment and are good tool for improving common bean production in regions with contaminated soil.