This study was designed to identify personality factors that underlie concern for ecological-environmental problems. High and low environmental-concern individuals were given the California Psychological Inventory and were found to differ significantly on many subscales. A factor analysis of the CPI data produced four factors which closely paralleled previous CPI research findings. In conjunction with this analysis, four factorially derived scores were obtained for each individual. Comparison of high and low environmental-concern individuals' factorially derived scores showed high environmental-concern persons as having stronger value orientation, person orientation, and ethical-conscientiousness, but not differing from low environmental-concern individuals in terms of independence of thought or action. Further, high environmental-concern females were found to be significantly more extraverted, “leader-types” than low environmental-concern females; while the opposite relation was obtained for males. Thus, it appears that men and women become involved with the environmental movement for different reasons. Finally, additional implications of the involvement of basic psychological individual differences in determining ecological-environmental concern were discussed.