There is evidence in California of a broad decline in health care costs to employment groups adopting managed care and managed competition--premium reductions up to 10 percent. National comparisons and utilization data generally confirm the beginning of lower costs. Large California medical groups and health systems have responded to pressure by finding ways to reduce costs and improve quality. While examples are encouraging, there is room for improvement. Two levels of competition have emerged and continue to evolve: carrier competition and delivery system competition. Each model has strengths and limitations, but the existing mix is driving down costs.