Tc-99m methylene diphosphonate (MDP) was prepared using stannous methylene diphosphonate (ligand) kits of similar formula from either of two manufacturers (A or B), and physiologic saline of either regular dissolved oxygen content (RDO, 6.7 mg O2/l) or low (LDO, 3.8 mg O2/l). A resulting Tc-99m MDP dose was administered to each of 70 patients for bone imaging. The A + RDO combination led to greater film density in the bone image than did the B + RDO (p less than 0.05). However, use of LDO saline to reconstitute B improved bone-image density to equal that from A + RDO. Overall image quality with A + RDO was judged to be superior to that with either B + RDO (p less than 0.05) or B + LDO (p less than 0.01) by an investigator unaware of the particular DO and ligand combination injected. However, neither bone delineation nor soft-tissue radioactivity on images was judged to be different among the four combinations (p greater than or equal to 0.05). There was also no difference in soft-tissue radioactivity among the four combinations as revealed by image densitometry. Under the conditions of this study, the major differences in clinical performance between products A and B were only minimally affected by the O2 content of the saline used for reconstitution.