This study examined individual and system characteristics associated with access to methadone maintenance treatment (MMT) among Medicaid-eligible adults entering treatment for opiate use in Oregon and Washington. Logistic regression was used to examine the relative contributions of predisposing, need, and enabling characteristics on access to MMT. Although the number of methadone admissions increased in both states, access rates (the percentage of opiate-using adults presenting for treatment who were placed on methadone) declined after 1995. Adults in remote counties were one fifth to one tenth as likely to be placed in a methadone maintenance program than those living in counties with a methadone clinic. Other significant barriers to access included polydrug use, legal system referral, residence in a group home, lack of income, and homelessness. Factors promoting access included prior methadone use, pregnancy, and self-referral to treatment. These results suggest that more can be done to expand access to methadone maintenance.