Ground beetle activity in Iowa cornfields, fencerows, and 2 relict prairies was sampled by using pitfall traps. Of 94 species collected, 5 remain determined only to genus, and 16 are listed for the 1st time as collected in Iowa. The relative abundance or frequency of collection is compared with Kirk's 1971 report of carabid collections in South Dakota. There was a definite habitat preference by many species. All 90 specimens of Harpalus indigens Casey were from the prairies. Evarthrus alternans Casey was most abundant in the prairies. Bembidion quadrimaculatum (L.) and Pterostichus chalcites (Say) were the most frequently collected species in the cornfields. By contrast, P. lucublandus (Say) was collected with almost equal frequency in all 3 habitats. Chlorinated hydrocarbon residues may have both a negative and positive effect on different species of ground beetles.