P>Background Methotrexate and fumarates are effective systemic therapies for moderate to severe psoriasis according to the European S3 guidelines. Objectives We conducted a randomized controlled trial comparing the effectiveness and the adverse events of methotrexate and fumarates. Methods Sixty patients with moderate to severe psoriasis vulgaris were randomly assigned to treatment for 16 weeks with either methotrexate (30 patients; 15 mg per week) or fumarates (30 patients; 30 mg, followed by 120 mg according to a standard progressive dosage regimen) and were followed up for 4 weeks. The primary endpoint with respect to the efficacy was the difference in mean change from baseline in Psoriasis Area and Severity Index (PASI) after 12 weeks of treatment. The study was powered to detect a difference of five points. Analyses were by intention to treat. Results Six patients were excluded because five were not eligible and one withdrew consent. Two patients in the methotrexate group and one in the fumarate group dropped out during the 12 weeks of treatment because of nonappearance at the outpatient clinic. In total, 25 patients in the methotrexate group and 26 in the fumarate group were evaluated in the primary analysis. After 12 weeks of treatment, the mean +/- SD PASI decreased from 14 center dot 5 +/- 3 center dot 0 at baseline to 6 center dot 7 +/- 4 center dot 5 in the 25 patients treated with methotrexate, whereas it decreased from 18 center dot 1 +/- 7 center dot 0 to 10 center dot 5 +/- 6 center dot 7 in the 26 patients treated with fumarates. After adjustment for baseline values, the absolute difference (fumarates minus methotrexate) in the mean values at 12 weeks was 1 center dot 4 (95% confidence interval -2 center dot 0 to 4 center dot 7; P = 0 center dot 417). Conclusions In this randomized trial methotrexate and fumarates were found to be equally effective in the treatment of patients with moderate to severe psoriasis. No serious or irreversible adverse events were observed in any of the patients.