Objective: Although numerous studies have demonstrated a socio-economic gradient in health, there is still a lack of research about the mechanisms behind this gradient. The aim of this study was to analyse possible mechanisms from adolescence to adulthood to explain the socio-economic gradient in somatic symptoms among men and women in the Northern Swedish Cohort. Study design: A prospective cohort study was performed, in which all pupils (n = 1083) in the last year of compulsory school were followed for 14 years. The response rate was high, with 96.6% still participating after 14 years. The data were mainly collected through repeated comprehensive self-administered questionnaires. Methods: The main dependent variable was a combination of socio-economic position and somatic health at 30 years of age. Multivariate multinomial and bivariate logistic regression analyses were undertaken. Results: After controlling for parental working-class position and health-related selection, the authors identified mechanisms from adolescence to adulthood for the socio-economic gradient in health that were related to social relations (poor relationship with father and unemployed friends among men, violence among women), labour market experiences (unemployment among men and women, physically heavy work among women), economic hardship (among women) and poor health behaviour. Conclusion: These analyses contribute to the development of epidemiological methods for analysing mechanisms for the socio-economic gradient in health. (C) 2011 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.