The prevalence of breastfeeding in France is one of the lowest in Europe: 65% of infants born in France in 2010 were breastfed when leaving the maternity ward. Exclusive breastfeeding allows normal growth until at least 6 months of age, and can be prolonged until the age of 2 years or more, provided that complementary feeding is started after 6 months. Breast milk contains hormones, growth factors, cytokines, immunocompetent cells, etc., and has many biological properties. The composition of breast milk is influenced by gestational and postnatal age, as well as by the moment of the feed. Breastfeeding is associated with slightly enhanced performance on tests of cognitive development. Exclusive breastfeeding for at least 3 months is associated with a lower incidence and severity of diarrhoea, otitis media and respiratory infection. Exclusive breastfeeding for at least 4 months is associated with a lower incidence of allergic disease (asthma, atopic dermatitis) during the first 2 to 3 years of life in at-risk infants (infants with at least one first-degree relative presenting with allergy). Breastfeeding is also associated with a lower incidence of obesity during childhood and adolescence, as well as with a lower blood pressure and cholesterolemia in adulthood. However, no beneficial effect of breastfeeding on cardiovascular morbidity and mortality has been shown. Maternal infection with hepatitis B and C virus is not a contraindication to breastfeeding, as opposed to HIV infection and galactosemia. A supplementation with vitamin D and K is necessary in the breastfed infant. Very few medications contraindicate breastfeeding. Premature babies can be breastfed and/or receive mother's milk and/or bank milk, provided they receive energy, protein and mineral supplements. Return to prepregnancy weight is earlier in breastfeeding mothers during the 6 months following delivery. Breastfeeding is also associated with a decreased risk of breast and ovarian cancer in the premenopausal period, and of osteoporosis in the postmenopausal period.