A monitoring program for a recently introduced vinegar fly, Drosophila suzukii Matsumura, 1931, was conducted in south-central Washington State, U.S.A. from March 2011 to November 2013. Along with D. suzukii, a complex of nine additional Drosophila Fallén, 1815 species were captured in baited traps and identified to species. The Drosophila were captured in Nalgene^® and Haviland traps baited with apple cider vinegar or a sugar yeast mixture that were distributed among seven different horticultural crops or unmanaged habitats. All flies captured were identified to species and quantified for each sampling period. The species identified and quantified included D. busckii Coquillett, 1901, D. funebris Fabricius, 1787, D. hydei Sturtevant,1921, D. immigrans Sturtevant, 1921, D. melanogaster Meigen, 1830, D. simulans Sturtevant, 1919, D. obscura Fallén, 1823, D. subobscura Collin, 1936, D. subquinaria Spencer, 1942 and D. suzukii. The predominant species in 2011 were the obscura group and D. hydei. In 2012, the predominant species were the melanogaster and obscura groups. The predominant species in 2013 were the melanogaster group and D. suzukii. Throughout the study, each species exhibited unique patterns in activity that varied from year to year. The results of this study reveal a greater diversity of Drosophila in the inland Pacific Northwest, U.S.A. Holarctic shrub-steppe environment than previously documented, highlighting the need for more in-depth research on any competition between D. suzukii and local Drosophila species.