Extensive sampling of the granitic plutons in Yosemite National Park, California, led to the retention of nine sites distributed in three plutons (Gateway, Sentinal, Half Dome) ranging in age (K-Ar) from about 89 to 79 million years (early Upper Cretaceous). Many specimens are unstable; they carry, in addition to their thermal remanence, a ‘random’ component of unknown origin. Mean directions for large numbers of specimens seem, however, to be significant. The mean pole for that time falls at 73.5°N, 174°E, in agreement with previous results. Virtual poles for the several sites are scattered with an angular deflection factor δ = 10.2°; they appear to show a clockwise (east to west) rotation of the geomagnetic pole about the mean rotational pole with a period of 105 to 106 years. There are some indications that the secular variation is not entirely smoothed out in a time of the order of 105 years.