This paper argues that nursing theories ideosyncratic to situations should be developed through research, if nursing practice is to be effective in achieving the objective of promoting, maintaining, or restoring health of clients / patients. After reviewing (1) the interactive relationship between the theory and research, (2) the type and sequence of research for theory- building, (3) the hierarchy of theories, and (4) congruence between the type of theory and research approach, it suggests (1) that more exploratory studies (research) should be undertaken as a way to develop descriptive theories that may lead to new hypotheses, (2) that more empirical studies should also be undertaken to test if new hypotheses generated from exploratory studies may be useful in the setting of nuring practice, (3) that more studies should be undertaken to develop useful measures of nursing concepts, and (4) that more replicated studies should be undertaken in order to give rise to the external validity of new theories. It also discusses the ethical considerations of nursing research in the future.