Breast feeding of premature, new-born babies is often difficult when they become sick and are transferred to a children's hospital. The mother's milk should be collected and provided to the child without a loss of quality or too high a bacterial count which could endanger his health. We collected 113 samples of milk using electric vacuum breast pumps and then determined the bacterial contamination. In most cases there was evidence of bacteria normally found on the skin although more than 10(5)/ml of these bacteria were found in only 11.5% of the samples. As potentially pathogenic germs gram-negative bacilli, beta-hemolytic Streptococci Group B and Staphylococcus aureus were found. The electric pumps were cleaned with two different methods: the usual technique (Series I: 41 samples) and second, sterilization or replacement of the various external pump components between the collection of individual milk samples (Series II: 72 samples). The total of bacteria was considerably reduced by these additional hygienic measures; 62.5% of the samples could now be given to the children unpasteurized whereas the former figure was only 29.3%. On the other hand there was no decrease in the number of milk samples containing either beta-hemolytic Streptococci (Group B) or more than 10(5)/ml bacteria normally found on the skin.