In the State Laboratory of North Rhine-Westphalia for Food, Pharmaceutical and Environmental Chemistry (Chemisches Landesuntersuchungsamt), more than 600 individual human milk samples have been analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), and more than 1400 individual milk samples have been analyzed for organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) since 1984. All samples were collected on a voluntary basis from nursing mothers mostly living in North Rhine Westphalia, a federal state in Germany. The samples analyzed so far show a typical pattern of PCDDs and PCDFs. Out of the 210 possible congeners, only those with 2,3,7,8-chlorine substitution were found. While OCDD normally shows the highest concentration, the levels of the other dioxin congeners decrease with decreasing number of chlorine atoms. A different pattern was found for PCDFs. Within this group 2,3,4,7,8-P5CDF is the most abundant congener, followed by the hexachlorodibenzofurans. The mean level of tetrachlorodibenzodioxin (TCDD) was found to be of 3.2 pg/g on a fat basis and for total PCDDs and PCDFs, calculated as I-TEq (NATO/CMMS), 29.3 pg/g on a fat basis. The investigations of the past 2 years have revealed somewhat lower levels compared to former years. This might be an indication that the efforts undertaken to minimize dioxin emissions and to shut down known sources have already had an effect on the body burden of humans. Although mostly banned for a considerable period of time now, some lipophilic persistent pesticides such as DDT, dieldrin, hexachlorobenzene (HCB), and hexachlorocyclohexanes (HCH) can still be found in human milk.(ABSTRACT TRUNCATED AT 250 WORDS)