Objectives: To demonstrate that pharmacists working with physicians and other providers in an ambulatory care setting can improve glucose, blood pressure, and lipid control for patients with type 2 diabetes and to report patient adherence to screening and general preventive measures. Design: Prospective, randomized, clinical practice study. Setting: Burlington, MA, between January 2001 and August 2003. Patients: 164 patients patients with type 2 diabetes older than 18 years with glycosylated hemoglobin (A1C) greater than 8%. Intervention: Pharmacist-patient clinic visits included obtaining a comprehensive medication review; performing targeted physical assessment; ordering laboratory tests; reviewing, modifying, and monitoring patients' medication therapy and providing detailed counseling on all therapies; facilitating self-monitoring of blood glucose; and providing reinforcement of dietary guidelines and exercise. Main outcome measure: Effect of clinical pharmacists working with physicians in an ambulatory setting on health measures (e.g., A1C, blood pressure, cholesterol) of patients with diabetes. Results: Baseline characteristics were similar between the two groups. After 1 year, significant improvements occurred for A1C and low-density lipoprotein (LDL) cholesterol in the intervention group compared with the control group (A1C, 7.7% vs. 8.4%; LDL, 93.7 vs. 105.1 mg/dL; P < 0.05). Systolic blood pressure improved for all study patients without a difference between the two groups. Diastolic blood pressure improved significantly in the intervention group compared with the control group (73.4 mm Hg vs. 77.6 mm Hg, P < 0.05). Significantly more intervention patients were screened for retinopathy, neuropathy, and microalbuminuria than control patients (P < 0.05). Conclusion: For all indices measured, this study demonstrated that collaborative diabetes management with a clinical pharmacist can improve overall care.