Ground beetles (Coleoptera: Carabidae) are important generalist predators that contribute to the natural control of pest species. These beetles have been found to be both abundant and diverse in many temperate agroecosystems, and to respond positively to low disturbance tillage systems. However, the most common method for sampling ground beetles, pitfall trapping, is biased by many variables that are influenced by crop-cultural practices, complicating the interpretation of results from such studies. Pitfall trap sampling was conducted during 2000-2002 to assess the activity-density and diversity of ground beetles across crops and tillage systems of the Palouse region of Idaho. A tandem mark-recapture study was conducted in 2003 to determine the extent that gender and tillage influenced the capture efficiency (CE) of traps for several numerically dominant species – Poecilus scitulus,Poecilus lucublandus and Pterostichus melanarius - captured during the 2000-2002 studies. Ground beetle diversity was found to differ by crop and tillage system, as was the activity-density of the numerically dominant ground beetles. The mark-recapture study indicates that trap CE for these species is not influenced by gender, but is differentially affected by tillage within and across crops. Activity-coefficients that account for CE bias and allow for the adjustment of activity-density patterns are provided.