There is an increasing trend in Australia and elsewhere for mothers to express breast milk. The purpose of this study was to explore breastfeeding women's experiences of expressing breast milk. An anonymous online questionnaire was sent to Victorian members of the Australian Breastfeeding Association via an e-mail link. Response fraction was 903 of 3024 (29.9%). The most common reason for expressing milk was to "store extra breast milk" (57%, 479/836). The most important reason was "not enough milk"/"to make more milk" (15%, 118/771). The majority of women (65%, 666/843) used an electric breast pump, and this method of expressing was preferred by 59% (454/769) of women. Adverse effects of pumps were pain (17%, 126/737) and damage to nipples (11%, 86/737). Breast pumps may have a role in enabling women to extend the duration of breast milk feeding, but further research is needed.