In seven of eight patients with osteoporosis circumscripta of the cranial vault, the pagetic bone lacunae were separated from the normal bone by a lucent rim visible on conventional radiographs and computed tomography scans. The contour of the rim was sharp on the side of the healthy surrounding bone and hazy on the side of the defect. To our knowledge, this sign has been reported in one single previous article dealing with two pagetic patients with the bisphosphonate escape phenomenon.