In order to have a better understanding of the reproductive performances of herds like those at Mirecourt, this review will specify the relationships between nutrition and reproduction in dairy cattle. Energy balance is considered to be the first nutritional factor to be analysed. Its estimates based on the calculation of the difference between the energy ingested and the energy needed are often difficult to obtain and lack precision. But other estimation methods do exist, taking advantage of the physiological consequences of a negative energy balance : measures of body condition score, analyses of milk compostion, or measures of physiological parameters. Reproductive performances also need to be described using well chosen parameters allowing a distinction as clear as possible between the different causes of impaired performance : abnormal delay to recover an ovarian regular cyclicity, or lack of fertility, either due to failures in fecundation or to embryonic losses. Statistical analyses generally conclude that a severe energy imbalance leads ta a delayed recovery of cyclicity and sometimes to poor fertility too. These links are explained by physiological hypotheses. Finally, some approaches are suggested to improve the situation. In particular, the impact of milk production and its management on the reproductive performances is discussed.