Vertebroplasty using polymethylmethacrylate (PMMA) for augmentation is accepted as a safe and effective treatment for vertebral compression fracture. However, various complications related to PMMA vertebroplasty have recently been reported. We experienced three cases with progressive collapse of PMMA-augmented vertebra. Collapse progressed after augmentation in cases where PMMA conglomerated without contiguous bone interdigitation. A high viscosity of the PMMA preparation and vertebral body cavitory lesion may play a role in progressive vertebral collapse. To avoid this complication, bone cement should be injected sufficiently and permeate to contiguous bone to create strong support and anchorage.