It had been the aim of the present study to characterize, on the one hand, the PBDE background exposure in Germany and to assess whether any health risks could be involved in PBDE intake by the infant through breastfeeding. On the other hand, it had also been intended to test the influence of the mother’s diet and of breastfeeding in the context of 2 study hypotheses since no unambiguous evidenve had been available so far in literature. For this purpose, a special study design was developed including 2 groups of participants, i.e. omnivores and vegetarians, and 2 defined sampling times. The numbers of samples required for testing of the study hypotheses had been derived by statistical methods in advance.