The field of volcanology has expanded greatly in the years 1967–1970, and work on active volcanoes has kept pace with this expansion. I have restricted this summary and the accompanying bibliography to studies by U.S.-based investigators of active or potentially active volcanoes. I have been immeasurably aided in writing this summary by communications from R. Citron of the Smithsonian Institution Center for Short-Lived Phenomena, W. Melson and T. Simkin of the Smithsonian Institution, A. McBirney of the Center for Volcanology, University of Oregon, R.B. Forbes of the University of Alaska, and R.W. Decker of Dartmouth College.