This study evaluated the relative effectiveness of natural attenuation and in-situ biostimulation of soil contaminated with weathered diesel fuel at two remote locations (Pony Creek and Birch Mountain) in the boreal forest of northeastern Alberta. Treatments included control unfertilized, control fertilized (N-P-K), contaminated unfertilized and contaminated fertilized (N-P-K) from 1998 to 2000. At Pony Creek, hydrocarbon levels decreased 4% with natural attenation and significantly (46%) with biostimulation. Hydrocarbon levels did not decrease at Birch Mountain during 1998 to 2000, possibly due to low soil moisture, but decreased 30% in 2001 with biostimulation. Fertilizer application stimulated an increase in soil microorganism populations and vegetation canopy cover and altered taxa composition of both microorganisms and vegetation canopy. Pasturella multocida , an aerobic bacteria that has not been previously identified as a hydrocarbon degrader, was isolated from the contaminated soil. Agrostis scabra Willd. (tickle grass) increased significantly with fertilizer application in the contaminated treatments.