The objective of this study was to describe sociomedical determinants and developments for the medically based disability pension in Norway by linking individual based data from a county health survey to data on disability from the National Insurance Administration. Two cross-sectional total population health surveys with an approximate 10-year interval were conducted in Nord-Trøndelag county, HUNT I (1984-86) and HUNT II (1995-97), which allows for analyses of changes over time, supplied with official incidence data on disability pension. The large-scale variations and overall increasing incidence rates of disability pension in Norway during the last 20 years also applied to the county of Nord-Trøndelag. The prevalence of disability pension generally increased in the population from the mid-1980s to the mid-1990s. A striking finding was a consistent pattern of increasing prevalence of disability pension with decreasing socio-economic status and education. A geographic pattern for disability pension prevalence on a municipality level suggested that structural and cultural factors were important in determining the level of disability in society. Medical determinants alone cannot explain either the dramatic variations or the overall increased incidence rates of disability pension in the last two decades in Norway. The results demonstrate the importance of social, non-medical and contextual determinants for disability pension, how these determinants result in important prevalence differences by socio-economic status, and their impact on the level of disability in society.