The combined influences of three environmental factors (nutrients, current velocity and grazers) upon the early establishment of stream phytobenthic communities (initial 5 weeks) were investigated in North West England. Nutrients were found to be more influential upon communities than current velocity or grazing. In eutrophic conditions, growth rates and diversity were greater and community dynamics appeared to be ultimately controlled by the biotic process of inter-specific competition. In oligotrophic conditions, although there was a large colonization pool, the communities were dominated by two species. These species were most likely selected for their ability to efficiently assimilate nutrients which supported the concepts postulated by the harsh-benign hypothesis. Furthermore, the oligotrophic communities produced a higher total biovolume than the more diverse eutrophic communities. The increased amount of species turnover in the eutrophic, compared to the oligotrophic systems, may represent community stability, suggesting support for the diversity-stability concept.