The release of crude oil into a southern California river from an earthquake-related pipeline rupture resulted in an initial rise in TPH and total BTEX concentrations in the water column. No toxicity was observed in aquatic toxicity rests conducted with rainbow trout and threespine stickleback. Statistically significant differences noted in several of the indices of macroinvertebrate community structure at sites downstream from the oil entry location appeared to be due to confounding factors including the spill. The assessment of incident-related impacts was complicated by several earthquake-related phenomena.