Questions: How commonly and how quickly does low back pain reoccur in a cohort of people who have recently recovered from an episode of low back pain? What are the prognostic factors for a recurrence of low back pain? Design: Prospective inception cohort study with monthly follow-up for 12 months. Participants: A total of 250 patients who had recovered from an episode of low back pain within the last month. Outcome measures: The primary outcome was days to recurrence of an episode of low back pain. Secondary outcomes were: days to recurrence of low back pain severe enough to limit activity moderately, and days to recurrence of low back pain for which healthcare was sought. Results: Within 12 months after recovery, 69% (95% CI 62 to 74) of participants had a recurrence of an episode of low back pain, 40% (95% CI 33 to 46) had a recurrence of activity-limiting low back pain, and 41% (95% CI 34 to 46) had a recurrence of low back pain for which healthcare was sought. The median time to recurrence of an episode of low back pain was 139 days (95% CI 105 to 173). Frequent exposure to awkward postures, longer time sitting (> 5 hours per day), and more than two previous episodes were predictive of recurrence of an episode of low back pain within 12 months (p < 0.01). Conclusion: Recurrence of low back pain is very common, with more than two-thirds of individuals having a recurrence within 12 months after recovery. Prognostic factors for a recurrence include exposure to awkward posture, longer time sitting, and more than two previous episodes. Key words: Risk, Recurrence, Low back pain, Prognosis, Cohort studies