The quality of a cortical bone, as reflected in the bone mineral content, has been studied in rabbit tibiae during an experimental atrophy process, and following recovery and adaptation to increased loading. Atrophy of the bone was induced by a rigid internal fixation plate applied to the tibia for 12 weeks. During the process of recovery after the plate had been removed, the bone mineral content was studied by means of an ashing procedure. The bone mineral content per unit volume cortical bone remained unchanged both at maximum atrophy and during the subsequent process of recovery.