The effect of hyperbaric oxygenation (HBO) treatment on rachitic change was studied using 4-wk-old, 1-hydroxyethylidene-1, 1-bisphosphonic acid disodium (HEBP-EHDP)-induced rachitic rats. After treatment, the dry weight, ash weight, Ca and P content, and bone mineral density of the hind leg bones were measured in each rat. These parameters were significantly increased in the rats that were treated with HBO after HEBP administration compared with those parameters in the rats that received HEBP alone. However, there was no significant differences between the rats treated simultaneously with HEBP and HBO and those that were treated with HEBP alone. These results were consistent with radiologic and histologic findings. Marked calcification in the center of the growth plate was revealed in the rats treated with HBO after HEBP administration. We suggest that intermittent high-pressure pure oxygen has a beneficial effect on osteogenesis in rachitic bone but does not prevent rachitic change.