A change in the constants used in K-Ar dating and a significant increase in new data have made a recompilation and recomputation of data used to define the Late Cenozoic K-Ar polarity time scale highly desirable at this time. All available data in the range 0--5 m.y. have been recalculated using the refined constants, with 354 data points in this time interval now meeting the minimum criteria for acceptability. Recalculation of the major polarity epoch boundaries has yielded ages of 0.73 m.y. for the Brunhes-Matuyama, 2.48 m.y. for the Matuyama-Gauss, and 3.40 m.y. for the Gauss-Gilbert boundaries. A revised polarity time scale has been constructed based on available K-Ar data and information obtained from marine magnetic anomalies and deep-sea sedimentary cores.