We assessed the effects of spinal manipulative therapy (SMT) for acute low back pain using a systematic review. Twenty randomized controlled trials were identified (N = 2674), 6 of which had a low risk of bias. For the outcomes pain and functional status, there is low- to very low-quality evidence suggesting no difference in effect for SMT compared with inert interventions, sham SMT or as adjunct therapy and very low to moderate evidence which suggests no difference in effect when compared with other interventions. Data were particularly sparse for recovery, return-to-work, quality of life, and costs. Future research is likely to have an important impact on this assessment.