Sera from patients with systemic lupus erythematosus (SLE) contain antibodies to a number of nucleic acids. Antibodies to double stranded DNA have been found in patients with SLE, and their titer are generally associated with the disease activity. In this study, the sera from patients with SLE and other rheumatic disorders were examined for antibodies to double-stranded RNA in the major immunoglobulin classes by solid-phase radioimmunoassay employing polystyrene tubes coated with poly-L-lysine. The technique provided high specificity for the antibody to double stranded RNA. The anti-RNA antibodies were found not only in the sera of patients with SLE, but also from patients with other related diseases though less frequently.