The oil sands operations in northern Alberta are among the most modem in the world. However, because the operations are extensive and lie on either side of the Athabasca River, there are concerns that they will adversely affect downstream environments such as the Athabasca River, its tributaries, the Peace-Athabasca deltas and Lake Athabasca. Research and monitoring programs are now investigating hydrocarbon sources, fate, and time trends in these aquatic ecosystems. Natural hydrocarbon sources (oil sands) are numerous along the Athabasca River and its tributaries. Petrogenic hydrocarbons also are abundant in downstream lakes. Lower molecular weight compounds such as naphthalene and fluorene tend to increase in concentration from upstream sources to downstream depositional areas. There is little or no evidence of temporal trends of increasing PAH concentrations in sediment cores collected in Lake Athabasca and the Athabasca delta lakes, suggesting no or minimal impact from the oil sands operations. Some PAHs exceed interim sediment quality guidelines and some bioassay studies have shown evidence of toxicity, particularly in the Athabasca delta. However, there is no evidence that this is associated with the oil sands industry. The RAMP monitoring program will continue to assess the potential impacts of the oil sands industry on river, tributary and delta ecosystems.