Applied psychologists who provide services to nations composed of multiple and widely varied cultural groups face certain ethical dilemmas that would not arise in more homogeneous societies. These ethical dilemmas revolve around the concept of population generalizability, which refers to the applicability of research findings across different populations. In the realm of basic research, population generalizability remains a scientific concern, but in applied psychology it becomes an ethical issue. It is an ethical issue because the effects of a particular service, intervention, or policy cannot be predicted for populations different from the samples that yielded the research findings. Population sensitivity refers to an orientation that seeks to make services, institutions, or policies harmonious with the characteristics and values of diverse populations. Ethical dilemmas related to population sensitivity generally have to do with whether participation in the population-sensitive service entails separation from the mainstream group. A framework is needed to deal with these ethical dilemmas. Such a framework should include: (1) scrutiny of the evidence that justifies application to members of a specific population; (2) an examination of plausible rational justifications; and (3) the design of experimental applications intended to test the hypothesis of population generalizability. (Contains 64 references.) (SLD)