Benthic macroinvertebrates were collected with a Surber sampler at 1,970 sample sites Korea from 1997 to 2002. The Self-Organizing Map (SOM) was used for patterning and visualizing community patterns of macroinvertebrates in different taxonomic and functional groups. The SOM accordingly classified the samples according to geographical regions and degree of disturbances. Species abundance distribution was further analyzed to reveal the ecological states pertaining to the sample sites. The slopes of rank abundance were characteristically different in accordance to the taxonomic and functional groups. The patterns of species abundance were also efficient in revealing ecological state of communities where physico-chemical indicators could not be easily differentiated in stressful conditions. The feasibility of species abundance distribution was further discussed in revealing ecological water quality.