Petroleum diesel fuel spills on soil poses a threat to the environment and require remediation. Phytoremediation, the use of plants to remediate a soil, has been used successfully to enhance remediation. However, the potential for phytoremediation decreases as concentrations of phytotoxic contaminants in the soil increases. Biodiesel, diesel fuel synthesized primarily from soybean oil, contains fewer toxic compounds than petroleum diesel and may be less phytotoxic at comparable soil concentrations. The objective of this research was to compare acetylene reduction (AR) rates of Glycine max (soybean) grown in petroleum diesel (PD) contaminated soil to those grown in a blend of 80% BD and 20% biodiesel (BD), or 100% BD contaminated soil. The experiments were conducted in a greenhouse. Experimental units consisted of one liter pots. A loamy soil was contaminated with 10g diesel kg^-1 and placed in the pots. Soybean seeds were inoculated prior to seeding and five seeds were sown per pot. The pots were watered to approximately field capacity daily. Plants were destructively harvested 4, 6, and 8 weeks after planting to measure the rate of AR reduction from the various diesel treatments. Roots were placed in sealed vacutainers containing 10% acetylene by volume and the concentration of ethylene was measured after 1 hour using a GC FID. Results showed the greatest root biomass, number of nodules, and nodule biomass was measured from the soybean growing in the B100 contaminated soil. The greatest rate of AR was also observed from the B100 treatment. The data indicate that legumes may be able to fix nitrogen at greater rates in B100 than in PD or B20 contaminated soils. Further research is required to determine if the amount of N fixed influences biodegradation rates or if biodegradation would benefit from supplemental N.