OBJECTIVES: MBD secondary to cancer can result in serious and costly SREs.  The objective of this study was to characterise hospital burden associated with MBD and SREs following BC and PC in Spain.  METHODS: Data from IASIST’s Conjunto Mínimo Básico Datos (CMBD) hospital activity database (January 1, 2000-March 31, 2006) were analysed.  The CMBD database contains clinical and administrative data on hospital admissions at 187 public and private hospitals in Spain.  Patients with an index inpatient admission of female BC or PC (ICD-9 codes 174* and 185* respectively) between January 1, 2003 and December 31, 2003 were selected for analysis and followed until March 31, 2006 for subsequent admissions inclusive of MBD (ICD-9 198.5 or ICD-10 C79.5) and SREs (pathological fractures, spinal cord compressions, bone surgery).  Hospital length of stay (LOS) and inpatient costs were analysed by cancer type (BC or PC) and disease stage (index, MBD, or SRE).   RESULTS: A total of 10,090 patients were identified with BC and 7546 with PC.  The 3-year incidence rates/1000 hospital admissions, including  MBD diagnosis code and MBD&SRE diagnosis codes, were 94.7 and 20.0 for BC and 166.0 and 29.3 for PC.  Readmissions were consistent across both cancer types, with MBD+SRE patients having the greatest number of readmissions (BC: 66%; PC: 62%) compared to patients with cancer diagnosis only (BC: 32%; PC: 27%) and patients with cancer & MBD (BC: 58%; PC: 54%).  Additionally, patients developing MBD & SREs had greater mean total LOS (BC: 28 days; PC: 32 days) than those with cancer only (BC: 8 days; PC: 15 days), and those with cancer & MBD (BC: 18 days; PC: 22 days).  Mean cost of admissions increased as the disease progressed from cancer only to MBD&SREs for BC and PC patients (€2374 to €3757 and €3194 to €3585, respectively).   CONCLUSIONS: In general, Spanish patients with BC and PC, who develop SREs secondary to MBD consume greater hospital resources than those with cancer or MBD only.