The plains prickly-pear (Opuntia macrorhiza Engelm.) is more abundant and wide spread in Illinois than previous publications have indicated. Populations of this species appear to be restricted to windblown sand deposits, loess hill prairies, and limestone glades along the Mississippi River, and the upper and extreme lower parts of the Illinois River. The eastern prickly-pear (Opuntia humisfusa (Raf.) Raf.) is largely restricted to sand deposits along Lake Michigan, the Illinois and Kankakee Rivers, and rock ledges of southern Illinois. The fragile prickly-pear (Opuntia fragilis (Nutt.) Haw.) is currently known from Illinois at a sand prairie in the valley of the Mississippi River in Jo Daviess County.