A 3 × 2 × 2 factorial field experiment, organized in a randomized complete block split-plot with four replications, was conducted in 1994 to evaluate the effect of two plant growth-promoting rhizobacteria (PGPR) strains (Serratia liquefaciens 2-68 or Serratia proteamaculans 1-102) on nodulation, nitrogen fixation, and total nitrogen yield by two soybean cultivars in a short season area. The experiments were conducted at the Emile A. Lods Research Centre, McGill University, Macdonald Campus, Montreal, Canada, and performed at two adjacent sites. One site was fumigated with methyl bromide (50 g m−2). Another site was kept unfumigated. Co-inoculation of soybean with B. japonicum and PGPR increased soybean nodulation and hastened the onset of nitrogen fixation, when the soils were still cool. Total fixed N, fixed N as a percentage of total plant N, and protein and N yield were also increased by PGPR inoculation. AC Bravor tended to be more responsive to both PGPR treatments for total fixed N and N yields than Maple Glen, suggesting that inoculation with PGPR was more effective for cultivars with higher yield potentials.