Soil enzymes play an important role in soil microbial ecology by catalyzing innumerable reactions. Plant roots release extracellular enzymes into soils, or stimulate microbial growth, and thus microbial enzyme activities, through the release of exudates, mucilages, and root remains that stimulate microbial activity, biomass, and potentially soil aggregation. Phenol oxidase is one of several enzymes able to degrade recalcitrant phenolic material such as lignin. The objective of this experiment was to determine if different vegetation affected phenol oxidase activity in a model riparian site, and to assess the distribution of phenol oxidase by depth and aggregate size. We used a completely randomized experiment design with 3 replications of four different vegetation (bare soils, fescue, gamagrass, and weeds). The water table in the riparian system was controlled at ~0.3 m depth and soil depths of 0-15, 15-30, and 30-45 cm were studied. The results showed that there are relationships between phenol oxidase enzyme activity and aggregate size class (4.75-2, 2-0.25 and < 0.25 mm) as well as with soil depth.  Phenol oxidase activity increased with decreasing aggregate size and was significantly greater in aggregates < 2 mm diameter compared to aggregates 2-4.5 mm diameter. In terms of vegetation, the relative amount of phenol oxidase activity was: fescue > gamagrasss > weeds > bare soil. In fescue and gamagrass the pattern of phenol oxidase activity with depth was 0-15 = 15-30 cm >30-45 cm, but there was no significant pattern observed in weedy or bare plots. Our results indicate that there are vegetative, structural and spatial differences in phenol oxidase activity in these riparian soils.