Pain is a multidimensional experience that is a prominent feature of many musculoskeletal disorders. Despite its subjective nature, pain is a highly relevant complaint; hence, nothing should deter physicians from attempting to formally assess it. This Review summarizes the main aspects of pain measurement from a practical standpoint, with a specific focus on low back pain. On balance, for the assessment of pain intensity, categorical scales with verbal descriptors or numerical rating scales seem to be preferable to traditional visual analogue scales, although no single best measure can be recommended. Pain per se should be assessed, rather than surrogate measures such as analgesic use. Back and leg pain should be evaluated separately in patients in whom these conditions coexist. For assessing change, prospective measurements are preferable to retrospective reports. Pain is not synonymous with function or quality of life, and other tools covering these important outcome dimensions should complement the assessment of pain, especially in patients with chronic symptoms. Clinicians should be aware of the psychometric properties of the tool to be used, including its level of imprecision (random measurement error) and its minimum clinically important difference (score difference indicating meaningful change in clinical status).