The expression of breastmilk is an important strategy to enable mothers to continue exclusive breastfeeding. In some situations, for health or convenience, expressed breastmilk is required and infants fed this way still fall within the definition of exclusive breastfeeding. The aim of this study was to document the changes in rates of breastmilk expression between the first Perth Infant Feeding Study (PIFS I) in 1992-03 and PIFS II in 2002-03. The proportion of mothers expressing breastmilk peaked in the first six weeks, at 38% for PIFS I and 69% for PIFS II. The proportion of mothers who had expressed breastmilk had almost doubled in the decade between studies. The proportion of mothers expressing declined to about 28% of mothers at 22 weeks for PIFS II and slightly less in PIFS I. Breastmilk expression is a very useful skill to allow mothers to exclusively breastfeed until six months and should be taught to all mothers.