When testing young children in optometric practice, clinicians rely on the visual acuity measurement to rule out amblyopia and to identify improvements in visual acuity with treatment. However, it is important in this context that the tests applied are robust in order that measures of acuity are as accurate as possible. This article provides practical advice for optometrists and other eye care professionals managing paediatric patients. Using the evidence available in the scientific literature and her own clinical and research experience, the author discusses the options available for testing paediatric visual acuity in a clinical setting. She compares some of the tests available (including the Cardiff acuity test, the crowded Lea symbols, the logMAR crowded test, the crowded Kay picture test and the Sonksen logMAR chart) and evaluates the evidence base for the robustness of some commonly used visual acuity tests. Data relating to normative values for visual acuity at different ages and guidelines for what constitutes a significant interocular acuity difference are provided.