The Port Talbot interstade is a cool, long, nonglacial interval separating the Early from the Late or Main Wisconsin in the Lake Erie region. Recent test borings at its type locality, lithologic and palynologic investigations of the cores, and new radiocarbon dates suggest that this interval was considerably longer than previously assumed. It began more than 48 000 years before present (B.P) and ended, if the Plum Point interval is included, 24 000 years B.P.The entire nonglacial interval comprises two relatively warm episodes, with boreal climate (Port Talbot I and II), separated by a brief glacial readvance that reached Lake Erie from the north; 100 varves were deposited during this readvance. Another similar readvance separates the Port Talbot I beds from the Plum Point (?) sands and silts. Pine (Pinus) and spruce (Picea) pollen predominate throughout the section, with relative abundance of oak (Quercus) in the Port Talbot I green clay. The pollen assemblages are dissimilar from those of the Sangamon interglacial or postglacial in southern Ontario.