In a randomized, placebo-controlled, double-blind study, glatiramer acetate (Copaxone®) reduced the relapse rate and slowed accumulation of disability for patients with relapsing-remitting multiple sclerosis. Of the original 251 patients randomized to receive glatiramer acetate or placebo, 208 chose to continue in an open-label study with all patients receiving active drug. The majority of the original double-blind cohort continues to receive glatiramer acetate by daily subcutaneous injection and are evaluated at 6-month intervals and during suspected relapse. The data reported here are from approximately 6 years of organized evaluation, including the double-blind phase of up to 35 months and the open-label phase of over 36 months. Daily subcutaneous injections of 20 mg glatiramer acetate were well tolerated. The mean annual relapse rate of the patients who received glatiramer acetate since randomization and continued into the open-label study was 0.42 (95% confidence interval (CI), CI=0.34-0.51). The rate per year has continued to drop and for the sixth year is 0.23. Of the group who have received glatiramer acetate without interruption for 5 or more years, 69.3% were neurologically unchanged or have improved from baseline by at least one step on the Expanded Disability Status Scale (EDSS). Patients who left the open-label phase were surveyed by questionnaire. The majority responded, providing information about their current status and reasons for dropping out. This study demonstrates the sustained efficacy of glatiramer acetate in reducing the relapse rate and in slowing the accumulation of disability in patients with relapsing forms of multiple sclerosis.