Macroinvertebrate communities were studied after a small dam removal in a Korean stream. Gokneung stream is 10 km north of Seoul in a rural area, near Bukhansan National Park. The dam (height 1.5 m, length 80 m) was removed April 2006. We sampled (Surber net 30 x 30 cm, mesh 0.25 mm, 4 duplicates per habitat) upstream (pool), dam-site, and downstream (riffle) habitats as well as a control habitat above the impoundment (ca. 300 m upstream from dam). Field sampling was conducted in March (before), June (after), September (after flood), and December in 2006. Environmental conditions, including substrate, were also surveyed during the field work. Benthic macroinvertebrate communities rapidly changed after dam removal and were correlated with microhabitat changes such as current velocity and substrate. Changes were greater in the upstream site than in other habitats for: species number (March 13 / September 21 spp.), McNaughton’s species dominance index (0.77 / 0.53), Shannon species diversity index (2.04 / 2.95), and group pollution index (1.92 / 2.00). Clingers and collector-filterers, such as hydropsychid caddisflies, considerably increased after dam removal. The flood in July 2006 enhanced the changes of microhabitats, which subsequently resulted in changes in benthic macroinvertebrate communities.