Evidence-based practice in health care requires that treatment decisions be supported by high-quality clinical evidence, preferably involving well-designed large-scale clinical trials of the various treatment options. How does this relate to everyday primary-care optometry? This article provides a background to the emergence of the 'evidence-based' movement and investigates areas where the efficacy of clinical optometry might be improved by an evidence-based approach. It is argued that evidence-based practice is appropriate for all aspects of optometry but it may be most useful in the selection of treatments with topical therapeutic agents and in optometry's growing public health role in the detection and management of sight-threatening disease.