The objective of the study was to examine whether the beneficial effect of treatment of interferon alfa-2a on multiple sclerosis seen by magnetic resonance imaging is reflected in a corresponding improvement in the quality of life (QoL) and to address the impact of adverse events related to this treatment on the QoL. The study was a randomised double-blinded placebo-controlled treatment trial including 97 relapsing-remitting multiple sclerosis patients. Thirty-two patients received 4.5 MIU recombinant interferon alfa-2a, 32 patients received 9.0 MIU recombinant interferon alfa-2a and 33 patients received placebo treatment for 6 months. All patients were followed up 6 months after end of treatment. QoL was assessed according to the eight scales of the SF-36 Health Survey and measured at baseline, month 3, 6 and 12. The effect found on MRI was not reflected in a corresponding change in the QoL. We found a relationship between the presence of new enhancing lesions and reduced QoL among the placebo patients, whereas this was not found among the patients treated with interferon. The presence of the adverse events fatigue, myalgia, headache and weakness were significantly negatively correlated to several of the QoL dimensions. Conclusively, the treatment with interferon alfa-2a does not seem to improve the patients' QoL after 6 months of treatment, in spite of a marked effect measured by MRI. The treatment is followed by adverse events that negatively affected the QoL.