Mixed cropping of two or more species is the most common form of production in areas where subsistence agriculture is the norm. Such systems are complex and frequently include legumes and cereals. Most agricultural research has focused on pure stand farming systems; therefore, there is a lack of research in mixed cropping, probably because in developed agriculture mixtures become more difficult to manage in the field, particularly when mechanization is introduced in extensive agriculture. However, some possible advantages of mixtures could be to produce more yield than when the component crops are grown separately because of a more efficient utilization of environmental resources, and better control of weeds, pests or diseases. It must also be emphasized that there could be some disadvantages of intercropping such as yield decrease of each individual crops due to competitive effects. The common bean is the third most important food legume crop worldwide (surpassed only by soybean and peanut) and it is the first one for direct human consumption. Beans are consumed mainly as a dry food legume, due to the high protein content of the grain, but the use of the fresh pod (snap bean) is common in many countries. The warm-season intercropping system of common bean and maize has been a common practice in Mesoamerica and South America, as well as in the south of Europe (Spain and Portugal). Sole cropping provides more seed in each cycle and allows better discrimination between varieties. Intercropping has less insect attack and the small farmer of limited resources often seems to have a strong preference for it. Therefore, the final product of a selection program in a specific system under these environmental conditions could be well adapted to both systems. The yields in an intercropping system are estimated by the ‘Land Equivalent Ratio’ (LER): the ratio of the area under sole cropping to the area under intercropping needed to give equal amounts of yield at the same management level, i.e. the sum of the fractions of the intercropped yields divided by the sole-crop yields. This index compares the productivity of the two cropping systems within a growing season or agrosystem using the formula: LER = La + Lb = Ya/Sa + Yb/Sb; where, La and Lb are the individual partial LERs for each crop, Ya and Yb the individual crop yields in intercropping and Sa and Sb the crop yields in sole crop. In most cases, researchers found that in the association of maize and bean the yield of both crops is affected by intercropping although maize yield is generally affected much less than that of bean. Some researchers reported LER values ranging 0.84-1.04 in intercropping of common bean and field maize in different environments in Spain and other researchers found LER values > 1.0 in Algeria, that support the advantage of this cropping system. Additionally, some observations indicate that it may be possible to increase both the symbiotic N-fixation and the seed yield through plant breeding in intercropping, a positive conclusion about the mixture of common bean and maize.