Hemipelagic sediments in Cascadia Basin were characterized by an abundance of planktonic foraminifers during glacial periods and by an abundance of radiolarians during interglacial periods. The relative abundances of these organisms are used to construct a paleoclimatic curve which includes several intervals indicative of cooling periods within the Holocene. These periods, from 5,000 to 4,000 and at 2,000 years B.P. appear to correlate with those reported in other paleoclimatic studies in widely separated localities.