Protozoan communities were sampled in 1978 from the South River near Waynesboro, Virginia, and compared with a study carried out in 1972. Five study stations were located above and below sources of pollution. Species richness followed the same pattern as in the 1972 study except at Station 2 (just below a major source of pollution) where a marked improvement in water quality occurred. Numbers of species increased significantly downstream from a source of pollution. This study provides evidence that protozoan communities may be used effectively in the assessment of water pollution and that results compare favorably with those based on macroinvertebrates which are more expensive to collect.