Paget's disease of bone (PDB) is a very rare disease in the Asian countries including Japan, although as a bone metabolism disease it is relatively common in Europeans and Americans. An infrequent complication of PDB is the giant cell tumor (GCT). We encountered a case of GCT in the maxilla complicating PDB in a 57-year-old Japanese woman. She developed her first GCT in the right occipital bone 14 years ago, which was resected. At the same time, she was given a diagnosis of polyostotic PDB. Four years ago, she developed two GCTs in the parietal bone, which were resected. Recently, she was found to have a GCT in the maxilla and maxillotomy was performed. The sporadic form of GCT associated with PDB almost always arises in pagetic bone. The clinicopathologic features of this rare lesion are described and correlated with a review of the literature.