Proposes that radial runout in a gear can contribute substantially to measured values of variations in profile@ pitch and index@ and in helical gears@ to tooth alignment (lead) variations. For each variation@ gives the equation that relates the measured value to the radial runout in an otherwise ideal gear. Demonstrates the relationship by comparing the result of actual measurement with the calculated value. Describes how the equations can: aid the interpretation of gear inspection data and explain differences between measurement methods.