This study uses the phosphorus index to estimate the relative impact of small proportions of the landscape on phosphorus pollution of surface waters.� The Minnesota Phosphorus Index (PI) is made up of three independent pathways used to characterize P delivery to a surface water body. The three pathways include 1) sediment-bound P from rainfall runoff, 2) soluble P from rainfall runoff, and 3) soluble P from snowmelt runoff.� The Minnesota PI was evaluated on 220 fields located within two watersheds in the south-central portion of the state.� Fifty-one percent of the study area had a PI site risk rating of low or very low (1 kg/ha/yr).� These areas are not deemed to be a significant risk for phosphorus pollution of surface water.� The remaining 32, 12, and 6% of the study area had a PI site risk rating of medium (3 kg/ha/yr), high (5 kg/ha/yr), and very high (7 kg/ha/yr), respectively.� Based on these estimates, 20%, 39%, 24% or 17% of the phosphorus loads at the mouth of the watershed can be attributed to fields with a very low or low, medium, high or very high PI rating, respectively.� Of particular interest is that 18% of the watershed area generates a disproportionate 41% of the phosphorus pollution.� Based on this information, implementing best management practices on a small proportion of the landscape (18%) should lead to large reductions in phosphorus loss to the mouth of the watershed.