The oligochaete fauna of 57 small streams of the Morava and Odra River basins, Czech Republic, was studied during 1997 and 1998. TWINSPAN and CCA (CANOCO) were used to characterize the relationship between oligochaete species, habitat diversity and environmental variables. Chemical oxygen demand (COD), water hardness, NO3--N, Ca2+, Mg2+, altitude, and substrate type were found to be primary factors influencing the distribution of aquatic Oligochaeta.