As the title states, the present document is a review of the factors which may influence the bean grain quality. This quality is determined by factors such as acceptability by the consumer, cooking characteristics and by its nutritive value. At the same time, these factors are affected by the genetic constitution of the grain as well as by the environmental conditions of production. Therefore, the improvement obtained on the bean-grain quality will be measured through the interaction established among the different disciplines, such as geneticists, agronomists and scientists in food science and nutrition. The above-mentioned factors are influenced by the events that occur in the different links of the food chain. This article analyzes the effect of processing on the nutritive quality of the grain and, likewise, a brief review of the hard-to-cook problem which affects the acceptability of the grain by the consumer is made. It also considers the low protein digestibility problem and the effects that have been associated to tannin content, as well as the carbohydrate utilization. Finally, some recommendations are suggested to improve the nutritional quality of beans, which is the most important protein source for large segments of the worldwide population.