Synthetic musks have a widespread use as a substitute for natural musks in fragrances, and can be found in a number of consumer products such as laundry detergents, cleaning agents and cosmetic products (soaps, perfumes etc.). The most frequently used synthetic musks belong to the nitro musks (e.g. musk xylene (MX) and musk ketone (MK)) and to the polycyclic musks (e.g. HHCB, AHTN, ADBI, ATII, AHDI) (Figure 1). Because of their high lipofility and chemical stability, musk compounds can be expected to accumulate in the human body, and it is important to investigate their occurrence in human milk. For risk assessment purposes, the Swedish NFA (National Food Administration) has made recurrent measurements of levels of selected persistent organic pollutants (POP) (e.g. polychlorinated biphenyls (PCBs), dioxins, persistent pesticides and flame retardants) in human breast milk. The ambition is to follow changes in the levels of these environmental contaminants in human breast milk and to establish a time trend. The aim is also to evaluate possible health risks for the mother and in particular for the breastfed infant. The first sampling of breast milk performed by the NFA occurred in Uppsala County in 1996-1999. About 300 primiparae participated in this large study that to some parts was financially supported by the Swedish EPA (Environmental Protection Agency). The second sampling was performed in Uppsala in 2000-2001 (n=31) and the third sampling in Uppsala in 2002- 2003 (n=31). A new sampling (2004-2005) is in progress. The investigations in 2000-2001, 2002-2003 and 2004-2005 have partly been financed by the Swedish EPA. Earlier (in 1999-2000 and 2002), 44 randomly selected breast milk samples from the monitoring of environmental contaminants have been analysed for synthetic musk compounds. The results presented in Eriksson et al. (2003) indicated that the levels of HHCB, AHTN and MX decreased from 1998 to 2001. The investigation also pointed to the possibility of a relationship between perfume exposure from cosmetics and detergents, and musk levels in breast milk. During 2003, 80 additional breast milk samples have been analysed for synthetic musk compounds. In this report results from the earlier (2002) and the latest (2003) analyses of nitro musks (MX, MK) and polycyclic musks (HHCB, AHTN, ADBI, ATII, AHDI) are presented. Results from the analysis in 1999-2000 have been excluded since the later analyses are of better quality. The total number of samples analysed in 2002 and 2003 is 101. The possible time trend and the possible relationship with use of perfumed products are investigated as well as relationships between musk levels and lifestyle factors such as age and body mass index (BMI). The analyses of musk compounds in breast milk and the compilation of data was financed by the Swedish EPA (Environmental Protection Agency).