Objective: To identify factors associated with exclusive breast-feeding and breastfeeding during the first year of life among Norwegian infants. Design: Data on breast-feeding practices were collected by a semi-quantitative FFQ. Setting: In 2006-2007 about 3000 infants were invited to participate in a populationbased prospective cohort study in Norway. Subjects: A total of 1490 mothers/infants participated at both 6 and 12 months of age. Results: Exclusive breast-feeding at 4 months was associated with parental education, parity and geographical region, while exclusive breast-feeding at 5?5 months was associated only with maternal age. At both ages, a negative association with exclusive breast-feeding was observed for maternal smoking. Breast-feeding at 6 months was associated with parental education, maternal age and marital status. Breast-feeding at 12 months was associated with maternal education, maternal age and number of children. At both ages, negative associations with breast-feeding were observed for maternal smoking and descending birth weight. At 12 months, a negative association was also observed for having day care by other than the parents. Conclusions: Even though Norway has an extensive and positive breast-feeding tradition and a maternal leave system that supports the possibility to breast-feed, factors like maternal education, maternal age and maternal smoking are strongly associated with duration of exclusive breast-feeding and breast-feeding. Research to better understand the reasons for inequalities in breast-feeding is needed to facilitate the development of more effective breast-feeding promotion strategies. This again may improve compliance with recommendations and reduce inequalities in infant feeding practices.Keywords Exclusive breast-feeding Breast-feeding Infant feeding practices Adequate nutrition during infancy and early childhood is essential to ensure growth, health and development of children to reach their full potential. Breast milk strongly contributes to good health and nutrition of infants. Apart from being an excellent nutritional source for the growing child, breast milk is associated with a reduced risk of many diseases in infants and mothers. A recent review by Duijts et al. (1) points out that a number of studies in industrialised countries suggest that breast-feeding protects infants against overall infections, gastrointestinal and respiratory tract infections. Moreover, Ip et al. (2) reported long-term benefits of breast-feeding for infants to be reduced risk of obesity and type 2 diabetes in later life, and long-term benefits for breast-feeding mothers to be reduced risk of breast and ovarian cancers.The initiation and duration of exclusive breast-feeding and breast-feeding are influenced by a number of factors. Although the factors that influence the initiation and duration of breast-feeding in developed countries have been broadly studied (3)(4)(5) , previous studies in these countries have rarely examined the factors associated with exclusive breast-feedi...