Abstract A six-step procedure was used to develop an instrument to predict environmentally responsible behavior in undergraduate students. One hundred eighty-seven examples of pro-environmental behavior were identified and classified into six different categories, and 15 undergraduate students at a major research university provided Thurstone-type judgments for each item. Students were asked to indicate the degree to which they felt the performance of each action was appropriate to a category of environmental action in which it appeared. The 144 items retained were pilot tested as two parallel 5-point Likert-type instruments with 828 students enrolled in an introductory biology course for nonscience majors. Development of the 28-item Environmental Action Internal Control Index (EAICI) incorporated SPSS-X techniques for correlational analysis, including factor analysis, regression analysis, and discriminant analysis. This instrument was field tested with another group of 853 students enrolled in the follow...