Aboveground shrub biomass was estimated in 34 shrub-dominated wetlands in northern Minnesota, representing a range of stocking. Salix was dominant in most wetlands, although a few were dominated by Alnus rugosa and Betula pumila. Shrub biomass ranged from 0.5 to 71.5 Mg ha-1 with an arithmetic mean of 11.2 Mg ha-1. Biomass was distributed lognormally among the wetlands, with a geometric mean of 6.9 Mg ha-1. Biomass estimates within wetlands had high uncertainty (10 to 85 percent of the mean) because of both clumpy distribution and large differences in size of shrubs. Eighty percent of the stands were on organic soils (Histosols), with two-thirds on minerotrophic and the remainder on weakly minerotrophic peatlands. Relationships of biomass to basal area and age were statistically significant. Differences in biomass were compared among wetlands grouped by soil or water chemistry. Stand age was a statistically significant covariate, but almost no significant differences in biomass were found among groups based on either criteria. Biomass of the shrubs in these wetlands was about four-fold greater than shrub biomass in mature forests in the area, but only slightly more than 5 percent of total biomass in those forests. These natural stands can be considered to set minimum boundary conditions for biomass production from wetlands. Forest Sci. 31:1011-1017.