Both storage of breast milk for 3 days at 4 degrees C and the addition of breast milk fortifier containing lipid improved the delivery of lipids during continuous pump infusion. The percentage of the original lipid delivered after 8 h of pumping was 9, 25, 58, and 66% from the freshly collected milk, stored milk, freshly collected milk mixed with fortifier, and stored milk mixed with fortifier, respectively. Phospholipid and cholesterol levels also were measured. Their loss during delivery through the tube was similar to the loss of total lipid. While storage improved the delivery of lipids from breast milk, the additional lipid delivered from milk mixed with fortifier was primarily due to lipids from the fortifier.