Book excerpt: Tables of cosmic-ray cutoff rigidities using the trajectory-tracing technique are given for three epochs of the geomagnetic field. These values have been determined utilizing the International Geomagnetic Reference Field with time derivatives applied so that the coefficients for the field model are appropriate for the following epochs: 1965.0, 1970.0, and 1975.0. Each table includes the geographic coordinates and L value of each location together with the main cutoff rigidity, the Stormer cutoff rigidity, and the effective cutoff rigidity. The altitude for which each set of values was calculated is also given. Tables for both vertical and non-vertical directions are included. These cutoff rigidity values are supplemental to those published in previous AFGL reports. In addition, minor corrections to previously published values are also included.