Medical practices that reside outside the mainstream medical structures have existed for centuries, often waxing and waning in prominence and use for various reasons. Recently, there has been a resurgence in interest and use of such practices in the USA generally referred to under the label of 'complementary and alternative medicine' (CAM). In this article we summarize some of the highlight events that punctuated this resurgence over the last 20 years. As in the past, social forces affecting these trends circulate around power, resources, and scope of practice. However, a prominent feature of this dynamic is a discussion about the role of science and 'evidence-based medicine' in addressing pluralistic healthcare-related practices. In the early years of this period, attempts to formulate the place of CAM practices as they relate to epistemology, nonconventional assumptions about health and healing, and the complexity of understanding 'whole systems' were discussed and often examined. Less attention is being paid to those core assumptions in more recent times. The focus now seems to be on how CAM practices can be judiciously and effectively 'integrated' into mainstream medicine. Examples of how this dynamic is evolving are described.