Seasonal activity of 24 species of ground-occurring, forest Coleoptera in northern Wisconsin and the Upper Peninsula of Michigan was assessed using pitfall traps during the spring and summer of 1996 and 1997. Overall, species richness, abundance and diversity remained relatively constant throughout the season, although species composition varied considerably. Trap catch of seven species was greatest from early May to late June: Calosoma frigidum Kirby, Carabus nemoralis Müller, Platynus decentis (Say), Pterostichus adstrictus Eschscholtz, P. mutus (Say), P. pensylvanicus LeConte and Sphaeroderus lecontei Dejean. Two species, Carabus sylvosus Say and Nicrophorus sayi Laporte, showed both early and late peaks in trap catch. Trap catch of eight species was greatest from early July to late August: Calathus ingratus Dejean, Synuchus impunctatus (Say), Pterostichus melanarius (Illiger), Pterostichus tristis (Dejean), Geotrupes bayli Jekel, Nicrophorus defodiens Mannerheim, N. tomentosus Weber and Oiceoptoma noveboracensis Forster. Implications for studies that assess impacts of forest management practices on beetle biodiversity are discussed.