PURPOSE: To describe the nationwide pattern of use of non-steroidal anti-inflammatory drugs (NSAIDs) in the Danish population. METHODS: All Danish citizens aged 10 or above 1 January 1997 were included in the study. The national prescription registry was used to identify all claimed prescriptions for NSAIDs by the cohort until 2005. By individual-level-linkage of nationwide registries, information was acquired concerning hospitalizations, comorbidity, concomitant pharmacotherapy and socioeconomic factors. RESULTS: The population consisted of 4,614,807 individuals, of which 2,663,706 (57.8%) claimed at least one prescription for NSAID from 1997 to 2005. Ibuprofen and diclofenac were the most frequently used non-selective NSAIDs, whereas rofecoxib and celecoxib were the most frequently used selective cyclooxygenase-2 (COX-2) inhibitors. The usage was similar across all age groups. Female sex and increasing age was associated with increased use of NSAID. Factors predicting extensive NSAID use were: rheumatic disease (odds ratio (OR) = 1.79, 95% confidence interval (CI): 1.69-1.90), gout agents (allopurinol) (OR = 2.54, CI: 2.44-2.64) and other pain medication (OR = 3.27, CI: 3.23-3.31). NSAIDs were most often prescribed for use for one distinct treatment interval and for a short period (overall inter-quartile range [IQR]: 9-66 days). High doses were used in a relatively large proportion of the population (8.9% for etodolac to 19.5% for celecoxib) and 54,373 (2.0%) claimed prescriptions for more than one NSAID at the same time. CONCLUSION: NSAIDs were commonly used in the Danish population. Since NSAIDs have been associated with increased cardiovascular risk, further research on the overall risk associated with these drugs on a national scale is needed.