The discourse about paths and instruments of sustainable development usually focuses on three strategies: efficiency, consistency, and sufficiency. There appears to be a broad consensus about the first two strategies. Efficiency aims at enhancing resource productivity while reducing resource use and it centers on technological innovations (cf. e.g. Weizsäcker, Lovins & Lovins “Factor four”, 1997). Consistency stresses the reorientation of production processes and material flows according to the constraints of the ecological system (change of industrial metabolism). Yet, there is growing awareness that those strategies are necessary but will not suffice in order to meet the goals and requirements for mastering global problems, such as reducing climate gases, stopping degradation of soils and of water resources. Therefore, many experts in the field of global environmental change stress the need for sufficiency as a third strategy for meeting the goals of sustainable development. The increase of energy efficiency, e.g., is counterbalanced by increasing needs and demands of a growing world population that strives for western standards of living (rebound effects). Sufficiency asks for “limits to growth”, a strategy that has been discussed as early as 1972 by the Club of Rome, although mainly focused on limits to population growth. Sufficiency involves principles , such as de-celeration, de-commercialisation (encouraging social services outside the labour market) and clearing-out (i.e., focusing on only necessary goods and services for a “good life”). Thus, sufficiency challenges the current norms and standards of models of well-being arguing for new patterns of consumption and for daily activities with reduced levels of affluence and consumption, for less mobility (or rather decreased use of personal cars with high levels of emissions), for the use of recycled, second hand, and repair-friendly endurable products (cf. e.g. the widely read report by Bund/Misereor “Zukunftsfähiges Deutschland/Sustainable Germany”. A study by the Wuppertal Institute for Climate, Environment and Energy,1996). However, a widespread discussion of the need for sufficiency and of ways to introduce this principle of sustainable development to a wider public has hardly begun. One of the reasons is that sufficiency is closely linked to the moral discourse about modesty, renunciation of resource use, contentedness, frugality etc. which is firmly based on norms and obligations (for future generations, for nature, etc.) This kind of discourse is presently not “in” and is not accepted by almost all groups within (western and industrialized) societies.Sufficiency needs to be introduced on various levels, from the macro level of society or even the planet as a whole down to the micro level of behavior patterns and life styles of individuals and small groups. Since behavior patterns and life styles are basically concepts of the social and behavioral sciences, psychology has to be involved.Although a comprehensive psychological model of sufficiency does not yet exist there are structural and dynamic models of environmentally relevant behaviors (such as the Theory of Planned Behavior, norm activation models, etc.) that stress variables, such as knowledge, habits, norms, attribution of responsibility etc. as determinants of behavior change. Other approaches focus on instruments, such as legal and economic, communication and diffusion instruments (cf. Kaufmann-Hayoz & Gutscher 2000 “Changing things – moving people”) to change behavior patterns, e.g. towards the use of car sharing. All these psychological approaches have not yet been integrated into the scientific discourse about sufficiency which so far has been dominated by sociologists, philosophers, and economists. Obviously, psychology has a “moral obligation” to enter the (still modest and restricted) discourse about sufficiency.