The profession of nursing has, in recent years, been trying to further develop, test and use proposed nursing theory. To utilize theory appropriately, in all domains of practice, education and research, it is important to know how to describe, analyze and evaluate theory. Evaluation of theory both within and among cultures should be a goal for the future of nursing to further advance the science of nursing. From a philosophical and historical standpoint, this paper attempts to define theory, including nursing theory, and then analyze criteria for the evaluation of theory. Finally, a more comprehensive set of criteria for the evaluation of theory is proposed, which may stimulate more informed decisions regarding the choice of nursing theory for use in practice, education and research, and from which may emerge new theories for and of nursing consistent with the 90s, and beyond.