Despite being recognised for many years as a clinical diagnosis, no exact definition of spinal stenosis has yet been agreed, leading to difficulties in interpreting and comparing studies of the incidence, prevalence and treatment. This study presents the first analysis of national data to be reported. It is a retrospective population-based national register study, aimed at analyzing surgical interventions in patients with lumbar spinal stenosis, patient characteristics, subsequent development, and case fatality rate, based on Swedish national data for 1987-1999. Complete follow-up data were obtained of incidence and type of spinal stenosis surgery, rate of multiple operations, mortality, underlying causes of death, length of hospital stay, and case fatality rate by linkage of the National Inpatient Register and Swedish Death Register. The study cohort consisted of 10,494 patients. Laminectomy was performed in 89%, and additional fusion in 11%. The mean annual rate of operations was 9.7 per 100,000 inhabitants, the annual number of operations performed increased from 4.7 to 13.2 per 100,000 inhabitants per year. The case fatality rate within 30 days after surgery was 3.5 per 1000 operations. Cardiovascular disease was the most common cause of death (46%). Relative risk of dying within 30 days of admission was doubled in men, and for fusion surgery, and increased four fold in patients older than 80 years. The relative risk of dying decreased during the study period. The results show that spinal stenosis surgery in Sweden has increased, and is associated with a low risk. Within an ageing group of patients, mortality has declined.