This report was based on a 25-year prospective cohort study and designed as a self-administered questionnaire with low back pain as the main topic. To identify whether radiologic changes in the thoracic and lumbar spine and a history of low back pain in the adolescent period represent risk factors for low back pain in adults. Six-hundred-forty 14-year-old school children were examined with x-rays of the thoracic and lumbar spine and registered by the school doctor regarding a history of low back pain. All of the x-rays and the short journals from the school doctor's registration were reviewed. This primary information was the basis of the investigation 25 years later. Eleven percent of the cohort had a history of low back pain in adolescence, and the results showed an 84% lifetime prevalence of low back pain in these subjects as adults and an increased frequency of low back pain the last month and week before they answered the questionnaire, compared with the rest of the cohort. These problems were associated with increased morbidity and decreased working capacity. Thirteen percent had radiologic abnormalities, mainly Scheuermann changes, in the thoracic and lumbar spine as adolescents, with no positive correlation to low back pain in this period. Unlike other reports, our results did not confirm a positive correlation between x-ray changes in the lower spine in adolescents and a higher prevalence of low back pain in adults. Stepwise logistic regression analyses showed that low back pain in the growth period and familial occurrence of back disease are important risk factors for low back pain later in life, with an observed probability of 88% if both factors are present. This study suggests that low back pain in the growth period is "a real problem," with a trend toward aggravation as time passes. Thus, implementing preventive measures in schools may be very important.