Infertility is a term which includes all reasons for cows not conceiving after breeding. Infertility results in either culling of the cow or increased calving interval which reduces overall production efficiency. Repeat breedings or anestrus are the most common signs ofinfertility. Causes of repeat breedings may include bull infertility, improper semen handling, poor estrus detection, a nutritional imbalance, incorrect timing of insemination, or a decreased fertility level in the cow. Nutritional imbalances are just one cause of infertility in dairy cattle, however, often more than one nutrient may be involved or other nonnutritional factors are partially to blame. These facts make it difficult to evaluate the effect of a single nutrient on infertility. Research previously indicated that nutrient requirements for high milk production was greater than that required for reproduction, (therefore cows fed for high milk production would receive adequate nutrients for reproduction). More recent research indicates slight deficiencies or imbalances of either major or minor nutrients may decrease fertility in apparently normal, cycling dairy cows. This paper will summarize the information available in the current literature about nutritional factors involved with infertility in dairy cows.