A randomized, double-blinded, placebo-controlled, clinical trial of low-dose, weekly, oral methotrexate was performed in 60 patients with clinically definite chronic progressive multiple sclerosis (MS) attending a referral-based outpatient MS clinic. Study patients were 21 to 60 years old with a disease duration of longer than 1 year. Patients' Expanded Disability Status Scale scores were 3.0 to 6.5 (ambulatory with moderate disability). Patients were first stratified by Expanded Disability Status Scale scores, 3.0 to 5.5 and 6.0 to 6.5, and then were randomized to receive methotrexate or placebo treatment. Treatment consisted of weekly, oral, low-dose (7.5 mg) methotrexate or identical placebo for 2 years, followed by observation for as long as 1 year. A composite outcome measurement instrument was used and consisted of (1) Expanded Disability Status Scale, (2) ambulation index, (3) Box and Block Test, and (4) 9-Hole Peg Test. Failure of therapy was indicated by a designated change that was sustained for more than 2 months in one or more components of this composite measure. Significantly less progression of impairment as measured by validated tests of upper-extremity function was observed in the methotrexate treatment group in the absence of clinically significant toxicity. We conclude that low-dose, weekly, oral methotrexate offers a new, relatively nontoxic treatment option for patients with chronic progressive MS.