Focusing on methadone maintenance treatment (MMT), this article evaluates the long-term treatment and follow-up of 245 clinical patients using high-dose methadone. Following a brief introduction describing the medical use of methadone in order to treat opiate addiction, the authors discuss the Center for Addictive Problems (CAP) MMT program. This study expanded on the authors' 1999 report comparing short-term treatment outcomes of 144 patients treated with high-dose methadone with 101 patients treated with regular doses of methadone. This current report details the treatment outcomes of the 245 patients at 152 weeks after the original data collection. Reviews of patients' urine toxicology reports indicate that the high-dose methadone group had significantly higher rates of retention in MMT than did regular-dose methadone patients. Furthermore, the high-dose patients had lower rates of positive urine toxicologies. The authors conclude that high-dose methadone treatment is not only safe for long-term usage, but is also particularly effective in treating patients with opiate addictions. Figures, table, references