The stoneflies of Illinois are reexamined more than fifty years after
the classic paper by Frison (1935). Nomenclature in Frison's paper con
cerning Illinois stoneflies is updated. Four species are deleted and s
ix species are added to the most recent North American species distrib
ution list. Additional species will be added when specimens of three P
erlidae species complexes are examined. Extensive collecting will cont
inue in an effort to verify the current status of the Illinois stonefl
y fauna.