Diabetes disease management programs (DDMPs) are proliferating, but their effectiveness in improving quality and mitigating health care spending has been difficult to measure. Using two quasi-experimental methods, this study analyzed the first-year results of a multistate DDMP for people with diabetes sponsored by a national managed care organization. In both analyses, overall cost of care were significantly lower in DDMP sites, and the payer saved more than it spent. Pharmacy costs showed mixed results. Quality scores in the DDMP sites were significantly better than in sites without the program.