Chiropractic is the best established of the alternative health care professions. Although marginalized for much of the 20th century, it has entered the mainstream of health care, gaining both legitimacy and access to third-party payers. However, the profession's efforts to validate the effectiveness of spinal manipulative therapy, its principal modality, have yielded only modest and often contrary results. At the same time, reimbursement is shrinking, the number of practitioners is growing, and competition from other healing professions is increasing. The profession's efforts to establish a role in primary care are meeting resistance, and its attempts to broaden its activities in alternative medicine have inherent limitations. Although patients express a high level of satisfaction with chiropractic treatment and politicians are sympathetic to it, this may not be enough as our nation grapples to define the health care system that it can afford.