The Cahaba River is a largely free-flowing river system in central Alabama noted for the great diversity of its aquatic fauna. Much of the vertebrate and molluscan faunas have been examined in past studies, but with the exception of the Trichoptera, relatively little is known of the aquatic insect fauna. This study was conducted to fill the void left by the absence of mayfly and stonefly data. Mayflies and stoneflies were collected from seven sites along a longitudinal gradient on the mainstem Cahaba River from late April 2004 to May 2005. Forty species, 25 genera, and nine families of Ephemeroptera were recorded. For the Plecoptera, 18 species, 10 genera, and four families were found. Six new state records for mayflies were recorded.