AbstractA total of 1136 Ephemeroptera, Plecoptera and Trichoptera were caught from March 1993 to March 1994 at the Weidlingbach, a first to fourth order forest brook near Vienna. Austria, using pyramid‐type emergence traps at tree sampling stations (390, 360 and 260 m above sea level). Five species comprised 67.1 % of the catch: the ephemeropteransParaleptophlebia submarginata(Stephens),Habroleptoides confusaSartori and Jacob andHabrophlebia lautaEaton, and the plecopteransNemoura flexuosaAubert andLeuctra hippopusKempny. Most taxa emerged from April to August, but the plecopteransLeuctra primaKempny andCapnia bifrons(Newman) were caught early in the year (January to April), andLeuctra digitataKempny (Plecoptera),Chaetopteryx fuscaBrauer andChaetopteryx majorMcLachlan (Trichoptera) emerged in September and October. In Ephemeroptera and Trichoptera, similarities between species groups were highest at the two upstream sampling stations; in Plecoptera and in pooled taxa, however, similarities were highest at the middle and downstream sites. Except in Trichoptera, diversity was highest at the middle station situated at 360 m above sea leve