Objective. The full panorama of the types and severity of low back pain during the life course is poorly known. We studied the incidence and severity of nonspecific and radiating low back pain based on a recent followup on a representative sample of the Finnish general population. Methods. As part of the ongoing Young Finns Study, participants ages 24 -39 years who were free from low back pain at baseline in 2001 were included (n ؍ 1,224). We estimated the incidence of nonspecific and radiating low back pain in 2007.Results. The incidence of moderate (8 -30 days duration in the past 12 months) nonspecific low back pain was 13.2%, and that of radiating low back pain was 8.6%. The rates did not differ between men and women. The incidence of major (>30 days in the past 12 months) nonspecific low back pain was 7.8%, and that of radiating low back pain was 3.4%. The incidence of major nonspecific low back pain was higher in women than in men (P ؍ 0.02). Moderate as well as major nonspecific low back pain declined with age, whereas major radiating low back pain increased with age. Conclusion. Our findings indicate that low back pain is a common condition in adults already in their 30s. It becomes more severe around the age of 40 years, showing different development of nonspecific and radiating low back pain. We recommend monitoring low back health in health surveillance, starting early and differentiating between nonspecific and radiating pain.