BACKGROUND AND PURPOSE: Little is known about how acute low back pain affects pelvic and lumbar movements during walking. The aim of the present study was to determine if measurement of the amplitude of the angular movements of the pelvis and lumbar spine during walking is useful in the evaluation of people with acute low back pain. METHOD: The study used a repeated-measures and correlational design; 11 individuals with low back pain (tested in the acute phase and six weeks later when symptoms had resolved) and matched control subjects were tested during treadmill walking. A video-analysis system was used to measure the amplitudes of movements of the pelvis and lumbar spine during walking. Pain level was measured with a visual analogue scale (VAS). RESULTS: During walking, movements of the pelvis (axial rotation) and lumbar spine (lateral flexion) were reduced in people with acute back pain compared with the resolved condition, but were not different from a group without a history of back pain. The amplitudes of the frontal plane movements of the pelvis and lumbar spine were negatively correlated with the intensity of pain (r(s) = -0.74). CONCLUSIONS: Measurement of pelvic and lumbar movements during walking is unlikely to have useful clinical applications for individuals, or when discriminating between impaired and unimpaired people, but may be applied to groups for hypothesis testing in evaluating change in back pain over time. An hypothesized model to explain the observed movements has been proposed.