Political efficacy has been studied extensively since the 1950s, hut analysts have never been fully satisfied with its measurement. After considerable testing, four new questions tapping internal political efficacy were added to the 1988 National Election Study. Our investigation shows that inter-item correlations among these questions indicate high internal consistency, that by both exploratory and confirmatory factor analysis the items measure a single concept distinct from external efficacy and political trust, that the measurement model is robust across major subgroups, and that the overall scale is externally valid and provides a good distribution of efficacy scores across the population. Further, the results of an order experiment in the survey suggest that responses are unaffected by mode of presentation. In short, the four new questions constitute the most satisfactory measure of internal political efficacy to date.