A 16-station seismic network was established in the Mount Hood area of Oregon in 1977 as part of a multidisciplinary study to evaluate the geothermal potential of a typical Cascade volcano. The immediate objective was to monitor local seismicity and to study the P wave velocity structure of the crust and upper mantle. During the 13 months the network was in operation, 10 local earthquakes were recorded. All these events are spatially associated with the volcano and occurred at shallow depths roughly defining a zone striking north-northwest. The largest earthquake, a magnitude 3.4 event, was preceded by a single foreshock and followed by three locatable aftershocks. These and the five other located earthquakes were of magnitude less than 2.0. Fifty-five teleseisms were recorded by the network and used in a teleseismic P wave delay study. The residuals from the P delay study indicate that there is no significant velocity anomaly associated with the Mount Hood volcano and only small velocity variations in the Mount Hood region.