The natural history of low back pain was evaluated over a nine year period in two groups of middle aged Dutch women selected from the general population. One group had recurrent back pain (n = 236) and the other group had never experienced back pain (n = 241). At the onset of the study recurrent back pain was associated with smoking, previous use of the 'pill', pain in other joints, frequent headaches, and restricted lumbar spine movement. Nine years later 170 (72%) of the group with back pain had continuing pain and 58 (24%) of the group without previous back pain had incident pain. Pain in other joints, especially the hip and knee, was a predictor of continuing and incident pain but age, body mass index, and smoking were not.