The objective of this study was to determine whether the supply of current photosynthate was limiting root nodule activity. Both short-term (36 hours) and long-term (16 days) periods of CO2 enrichment were imposed on vegetative, growth chamber-grown soybean plants (Glycine max. [L.] Merr. cv. `Clay') to increase the supply of current photosynthate and to observe the effects on photosynthate partitioning in the plants, plant growth, and root nodule activity.