OBJECTIVE: To discuss the immediate increment of improvement in vision that occurs when the spine is manipulated. CLINICAL FEATURES: Two juvenile patients (13-yr-old female cousins) were found to have constricted visual fields and diminished visual acuities. INTERVENTION AND OUTCOME: Spinal manipulation was associated with recovery of normal vision over seven treatment sessions. It was noted that significant improvement in vision occurred immediately after the spinal manipulation treatments. Full recovery of vision was attained by series of these steps. In addition, both patients reported significant constitutional benefits after the treatment in addition to the improved vision. CONCLUSION: The change in visual function immediately related to spinal manipulation has been described as the "step phenomenon." The step phenomenon raises questions about the nature of the condition that may be treated by spinal manipulation and the method of action of the treatment. A vascular hypothesis is mentioned that could explain these events. The consistent occurrence of the step phenomenon indicates that spinal manipulation may have an effect on brain function.