Examining trends and geographic variations in clinical care offers insights into changes in clinical decision making. We summarized data on spine surgical rates, trends, and variations in the United States to highlight areas of professional uncertainty and questions for future research. The United States has the highest rate of spine surgery in the world, but spine surgery shows wider geographic variations than most other procedures. For example, Medicare data for 2001 showed sixfold variations in spine surgery rates among United States cities, and 10-fold variations in spine fusion rates. United States spine surgery rates rose 55% in the 1980s. In the 1990s, studies of surgical rates became more difficult because 20% of discectomies shifted to an out-patient setting. Extrapolations from states with ambulatory surgery data suggest overall lumbar surgery rates continued to rise throughout the 1990s. The most rapid increase was for spinal fusion, which tripled during the 1990s and accounted for an increasing proportion of all spine procedures. Some increases coincided with the introduction of new surgical implants. Despite new technologies, rates of repeat surgery after fusion were no lower than the rates after decompression alone. As new technology for spine surgery is introduced at an accelerating pace, we anticipate substantial changes in surgery patterns. Analysis of population-based data may be useful for surveillance of changes and their impacts.