OBJECTIVES: To estimate the number of hospitalizations for severe hypoglycaemia (SH) in patients with diabetes mellitus in Spain and assess the differences amongst regions. METHODS: A retrospective study was conducted using the hospital Minimum Basic Data Set (CMBD) which collects up to 73% of all hospitalizations in Spain. All hospitalization episodes of diabetic patients in which SH was the principal or secondary diagnosis for hospitalization during 2007 were accounted for. A SH was defined as a hypoglycemic episode which requires hospitalization. RESULTS: The number of SH episodes as primary diagnosis was estimated at 8,242 in relation to total discharged patients with a diagnosis of DM2 (primary and secondary) at 496,660 patients (1.66% of total). When the number of SH as primary diagnosis is related to the total number of discharged patients with a diagnosis of DM2 as the primary diagnosis (23,343 patients), the percentage of episodes become 35.31%. The number of SH as a secondary diagnosis for hospitalization was estimated at 17,302 episodes: 16,649 in patients with DM2 (96.2%) and 653 in patients with DM1 (3.8%). For DM2 when SH as secondary diagnosis are added to primary diagnosis, the number of episodes is 24,891, which means that hypoglycaemia diagnosis accounts for 5.01% of hospitalizations for DM2 patients (496,660 patients).Catalonia shows the highest number of SH, with 1,477 episodes as a primary diagnosis in DM2 patients (17.9% of total) and 3,836 episodes of SH as a secondary diagnosis in DM2 patients (23.0% of total). CONCLUSIONS: : Severe Hypoglycemia represents a significant cause for hospitalization for DM2 patients in Spain: incidence of 1.66% estimated in the overall DM2 patients increases to 35.3% in the subpopulation of patients discharged for DM2 as primary diagnosis. There is a great variation in the incidence of severe hypoglycaemia between regions.