An open Phase I trial of poly(I,C)-LC in multiple sclerosis was conducted. Serious temperature elevations were typical and associated with transient accentuation of neurological dysfunction which required intensive nursing care, but no permanent complications to the treatment were observed. A regimen was developed for management of the side effects and reducing patient discomfort. Although there was a suggestion of stabilization of the disease in some patients, a conclusion about efficacy cannot be reached without a controlled trial. Future use of poly(I,C)-LC in multiple sclerosis should be confined to experimental trials in a research setting.