Hydrate Ridge is the location of unusually high concentrations of gas hydrates and was the site of Ocean Drilling Program (ODP) Leg 204 in the summer of 2002. It is located on the Oregon (USA) continental margin and is part of the accretionary complex formed by the subduction of the Juan de Fuca plate under the North American plate. The large concentrations of gas hydrates in this area make derivation of methane from local sources rather unlikely and raises questions about the potential source formations and pathways for the hydrocarbons and associated water. Because of the strong affiliation of iodine with organic material, together with the presence of a cosmogenic isotope, the iodine isotopic system is a powerful tool to determine source formations responsible for the release of hydrocarbons. We present here results of iodine and bromine determinations in a large set of pore water samples from all cores taken during Leg 204, as well as first results for 129I/I ratios in a subset of these samples.