Abstract: This work reports the distribution of a large, representative sample population of grain boundary plane crystallography in pure, annealed copper by use of an improved experimental procedure. The new methodology reduces the laboriousness and improves the accuracy of data collection, and so is described in detail. Analysis of the results concentrates on the Σ3 boundaries, and shows that three-quarters of these were tilt boundaries on the 011 zone. Of these tilt boundaries, nearly half were coherent twins, i.e., on 111/111 planes, or near coherent twins on 23,17,17/775 planes. The high population of the second group is thought to be due to oxygen take-up during annealing. The data in general showed a trend for lower energy Σ3s to occur more frequently. The results were interpreted in terms of boundary energies, local equilibration, and comparisons with previous work in copper and other systems.