Lake Maggiore (LM) is the second largest Italian lake in terms of volume, surface and depth, with the northern third residing in Swiss territory. The most important tributaries are River Ticino (Northern inlet) and River Toce (Western inlet). The River Ticino leaves LM at the southern end and connects LM to the River Po. Particular concern arose from the contamination with DDT and its metabolites, which exceeded Italian and EU levels for consumption in fish, and was detected in bird eggs from fish feeding species as well. As a consequence the local Health Authorities prohibited commercial fishing of a series of contaminated fish species. The source of DDT contamination was a DDT production site, closed down in 1996. This plant was located on the Marmazza River, a tributary of River Toce entering LM from the westernmost part of LM, close to Baveno. Besides the contamination with DDT, PCBs, including some dioxin like congeners, were found at concentrations exceeding 3-7 times the levels of other sub alpine lakes in Italy. Levels of HCB and HCH in the LM ecosystem instead gave no rise to concern. The aim of the present study is to supplement the existing data on POPs with sediment levels of PCDD/Fs, where so far only few data are available for LM. The PCDD/F concentration in the 50 surficial sediment samples taken at water depths between 5 and 60 m in LM display a broad range of concentrations, from 0.13 to 32 pg WHO TEQ g-1 d.w.. The PCDD/Fs show a consistent congener pattern. In the sample taken at the inlet of River Bardello the congener distribution was dominated by Octachloro- followed by Heptachloro-dioxins; the Heptachloro- and Octachloro –furans occurred at a level of only 0.80 pg WHO TEQ g-1 d.w..The spatial homogeneity of the pattern along the whole lake (Figure 2) underlines the absence of local sources and important riverine inputs into LM. Moreover, the pattern is similar to that of PCDD/Fs in atmospheric particulate matter and bulk deposition