The objective of this study was to compare the efficacy of a mini-electric pump (MEP) and a novel manual breast pump (MP) designed to operate more physiologically. Sixty term breastfeeding mothers used the MP and MEP in randomized order 8 weeks postpartum, expressing for 10 minutes from each breast. Milk volume, fat content, and pattern of milk flow were measured. Mothers rated pump characteristics by questionnaire. There was no significant difference in the milk volume or fat content when mothers used the pumps in randomized order. The MP was rated significantly better overall and more comfortable and pleasant to use. Significantly more mothers kept the MP than the MEP. Despite the greater complexity and expense of the MEP, the pumps showed similar efficacy. The MP was preferred by mothers. The novel, more physiological operation of the MP represents an advance in milk expression technology.