A gallocyanin method for demonstrating cement lines in thin, undecalcified sections of bone has been developed that is compatible with prestaining with ostcochrome before plastic embedding. After sectioning at 5 pm on the Jung K heavy duty microtome, the sections are attached to a microslide using Haupt's adhesive mounting medium, placed on a slide warmer at 37 C until completely dry, and deplasticized in xylene at 45 C for 16–44 hr. Sections are stained with 0.15% gallocyanin-5% chrome alum solution for 30 min, followed by staining in buffered Villanueva blood stain for 1–1 1/2 hr, quickly dehydrated, differentiated in equal parts xylene and 100% ethanol, cleared, and mounted in Eukitt's medium. Reversal lines appear as thin, scalloped, blue or purple lines approximately 0.3 pm wide, and arrest lines as thick, homogeneous, straight or evenly curved, dark blue or purple lines approximately 2 pm wide. The method also demonstrates abnormal halo volumes around ostcocytes, old and new bone matrix, osteoid seams, and the granular mineralization front at the osteoid-bone interface. It promises to be valuable in the study of age-related bone loss, osteoporosis, and metabolic bone disease.