Reappraisal of Alexander Thom's hypotheses on the spacing of stone rows, eliminating nonauthentic sites and using improved statistical techniques, indicates strong support for the use of the megalithic yard in their construction, this support not being confined to Scottish sites. The two sites in northern Scotland give strong evidence for a larger quantum, ca. 7 feet (megalithic rod?). This method should now be applied to the Brittany rows.