The objective of this study was to describe the problems experienced by mothers when breastfeeding and the impact that these problems have on breastfeeding duration. A cohort of 556 mothers who birthed in Perth, Western Australia were recruited to study their infant feeding practices. The mothers were interviewed in hospital and again at 2, 6, 10, 14, 18 and 24 weeks postpartum, or until they ceased to breastfeed. The results showed that most mothers were not prepared to experience any difficulties or problems with breastfeeding. Twelve percent of the mothers left hospital without having attempted to breastfeed. The most common reasons given for infant-formula-feeding related to previous problems with breastfeeding, the ability of husbands to assist with feeding and perceived ease of bottle-feeding. While in hospital 83% of breastfeeding women stated that they had experienced one or more problems related to breastfeeding. Two weeks after leaving hospital 29% of breastfeeding mothers were experiencing problems and the prevalence of problems continued to decline, reaching 13% at six months. In this study the most common reason cited by mothers for stopping breastfeeding before the baby was two weeks old, was that their baby was unsettled, a behaviour often interpreted by mothers as indicating an insufficient milk supply. Levels of anxiety over milk supply reached 23% in the early stages of breastfeeding, and a number of mothers were still experiencing anxiety through to six months. Anxiety over the sufficiency of breastmilk supply was the most serious problem, in that it often resulted in the cessation of breastfeeding Most mothers experience some problems during breastfeeding, especially in the early stages. Proper advice and management is required to ensure that the problems do not lead to cessation of breastfeeding.