The purposes of this study were to assess outcomes of patients prescribed buprenorphine at a primary care practice and to identify factors associated with favorable outcomes. All 255 patients given at least one prescription for buprenorphine between August 2003 and September 1, 2007, at a primary care practice in Baltimore were included. Data regarding demographics and comorbidities were collected retrospectively. Patients were classified as "opioid-positive" or "opioid-negative" each month based on patient report, urine toxicology, and provider assessment. After 12 months, 145 (56.9%) patients remained in treatment, and 64.7% of their months were opioid-negative. Patients using heroin were less likely to be opioid-negative, whereas those using prescription opioids were more likely to be opioid-negative. Polysubstance use was associated with increased treatment retention. The prescription of buprenorphine for opioid dependence treatment can be incorporated into primary care practice, and many patients, including polysubstance users, benefit from this treatment.