PURPOSE: We wanted to test whether improvements in care quality were correlated with changes in the Chronic Care Model (CCM) in a large medical group that attempted to implement the CCM. METHODS: The leaders of 17 primary care clinics in this medical group completed the Assessing Chronic Illness Care (ACIC) survey measure of CCM implementation before and after care system changes were made. We used administrative data to measure care quality changes for yearly samples of patients with diabetes, coronary heart disease, or depression. RESULTS: The total ACIC score for the CCM increased by an overall average of 1.4 points (from 5.8 to 7.2 on a scale of 1 to 11, P = .02) and significant increases occurred for 3 of the 6 components of the CCM. During this time, patients experienced a significant increase in the proportion meeting a composite outcome measure for low-density lipoprotein (LDL) and glycated hemoglobin levels (from 15.7% to 25.5%, P = .001). Heart disease patients meeting a composite measure for LDL values increased from 46.8% to 57.8%, and the percentage of patients with 1 or more cardiac events dropped from 17.2% to 11.4% (P = .001 for each). Persistent use of new antidepressants did not change, but more of these patients had follow-up visits (P = .02). Only the diabetes measure was significantly correlated with 2 CCM elements-clinical information systems and decision support. CONCLUSION: Despite implementation of the CCM and improvements in quality measures for 3 chronic diseases, there were few significant correlations between these changes. Showing such a relationship may require larger changes, a larger number of clinics, changes in other CCM elements, or a more-sensitive measurement tool.