The objective of this paper was to review recent studies on nutrient synchrony and the effects of synchronization of energy and N supply in the rumen on nitrogen utilization and animal performance. Theoretically, synchronization of energy and N supply in the rumen should allow more efficient use of nutrients by rumen microbes, increase microbial protein and fermentation end products, and thus increase available nutrients in the small intestine. Efficient use of nutrients possibly improves animal performance and reduces nutrient excretion to the environment. However, a number of studies showed contradictory results in microbial protein synthesis, nitrogen retention and animal production performance. Since there are additional challenges to nutrient synchrony that must be addressed, further research is required to apply the nutrient synchrony concept directly to the field situation.