Middle to Late Devonian paleomagnetic data from cratonic North America and Europe indicate that a 2,000-km sinistral displacement occurred between these two continents during Carboniferous time. Because the Lewisian basement of northwest Scotland and the Archean-Proterozoic basement in Greenland have strong geologic affinities, the fault(s) responsible for the displacement are likely to be found to the south of the northwestern Scottish Lewisian basement. In addition, published paleomagnetic directions for Middle to Upper Devonian rocks from the Orcadian Basin in Scotland give a mean pole near lat 50°N, long 150°E (A95 = 8.8°; K = 76.9; N = 5), which is in excellent agreement with the cratonic North American pole for this time, after closing of the Atlantic Ocean. A comparison between the Orcadian Basin results and those from areas to the south of the Great Glen fault in Scotland and England (mean pole near lat 31°N, long 152°E for Great Britain), reveals a paleolatitude difference of more than 15° for contemporaneous rocks and suggests that most of the commensurate sinistral motion between the North American craton and Europe took place along the Great Glen fault. Previous explanations for the Orcadian Basin results were cast in terms of implausible remagnetizations; some of the previous analyses can be shown to be incorrect.