Excessive drinkers (141) identified in medical settings who were not seeking help for an alcohol problem completed a questionnaire based on Prochaska and DiClemente's stages of change model. Principal components analysis revealed a clear factor structure corresponding to the 'precontemplation', 'contemplation' and 'action' stages of change. On this basis, a 12-item 'Readiness to change' questionnaire was developed with satisfactory psychometric properties. As predicted, scale scores on adjacent stages of change showed significantly higher inter-correlations than scores on non-adjacent stages. Concurrent validation by comparison with subjects' choices of cartoons depicting each of the stages of change and with screening questions regarding aspects of drinking behaviour was moderate to very good. The questionnaire provides a short and convenient measure of readiness to change which may be used in conjunction with brief, opportunistic interventions with excessive drinkers.