Twenty-eight species of Pselaphinae have been collected at the H. J. Andrews Experimental Forest: Sonoma cascadia Chandler, Sonoma conifera Chandler, Sonoma hespera Park and Wagner, Sonoma margemina Park and Wagner, Sonoma olycalida Park and Wagner, Sonoma parviceps (Mäklin), Mayetia smithi (Schuster), Oropus cavicauda Casey, Oropus micropthalmus Chandler, Oropus striatus (LeConte), Euboarhexius sinus Grigarick and Schuster, Trisignis marshi Park and Schuster, Abdiunguis fenderi Park and Wagner, Oropodes dybasi Grigarick and Schuster, Euplecterga norstelcha Grigarick and Schuster, Euplectus silvicolus Chandler, Actium barri Park and Wagner, Actium microphthalmum Park and Wagner, Actium retractum Casey, Cupila excavata Park and Wagner, Batrisodes albionicus (Aubé), Reichenbachia fusticornis Casey, Lucifotychus cognatus (LeConte), Lucifotychus dentatus (Grigarick and Schuster), Lucifotychus impellus Park and Wagner, Lucifotychus stellatus (Grigarick and Schuster), Pselaptrichus intimus Schuster and Marsh, and Pselaptrichus rothi Park. Twelve other species known from the Cascade Mountains of Oregon are included in a key to the species of this area. Species richness and abundance are discussed for the sixteen species taken during a two-year study of a series of sites representing different ages in a forest succession and plant associations/habitats. For drier sites species richness and abundance increase with the age of the forest; for moderately wet sites species richness is slightly higher for the youngest sites; and for the wettest sites species richness remains similar while abundance increases sharply after the herb stage and is similar for the older successional stages. Two species, O. micropthalmus and A. microphthalmum, both with small eyes, are most abundant in the tree and old-growth stages, and A. microphthalmum is clearly most abundant in old-growth forests. The species characteristic of old-growth or early successional stages are noted, as well as those typical of high or low elevations in the Cascade Mountains.