Background: Several forms of psychotherapy aim at improving their patients' emotional expressivity, which is considered to contribute to mental health. Studies on the success of such attempts are virtually absent. Aim: To develop a measure for assessing changes of emotional expressivity in the course of psychotherapy. Method: In study 1 (N = 321), we generated a pool of German adjectives referring to emotional expressivity and reduced the number of those adjectives by means of factor-analysis. In study 2 (N = 103), we determined how emotional expressivity is related to the Big Five personality factors. Results: An expressivity scale of 12 items with highly satisfactory psychometric properties was construed. Emotional expressivity is substantially related to Extraversion and moderately related to Agreeableness and Openness. Conclusion: The scale is ideally suited for repeated assessments in the course of psychotherapy in multi-agent (e.g., inpatient) settings. Copyright © 2007 John Wiley & Sons, Ltd.