We analyzed isoelectrofocusing (IEF) patterns of anti-DNA antibodies originated from sera and the renal eluates of patients with systemic lupus erythematosus (SLE). The spectrotypic patterns of serum anti-DNA-antibodies were heterogenous and bands with single-stranded (ss) and double-stranded (ds) DNA were detected in the PI 5.5-6.5 and 8-9.5 regions when SLE sera were tested, whereas healthy subjects failed to form bands even at different saline concentrations. No differences were found for IEF patterns of anti-DNA antibodies between patients with lupus nephritis and those without. The eluates from SLE glomeruli showed relatively restricted IEF patterns which were detected mainly in PI 6.0 and 8.5; but those from normal subject did not. These data indicate that anti-DNA antibodies will be responsible for the pathogenesis of lupus nephritis. Specific clonotypes of serum anti-DNA antibodies, however, could not be defined in an association with renal lesions of SLE. This study also suggests that the use of a high concentration of 6 M urea in an IEF analysis may be able to expose antigen-binding sites of the circulating immune complex (IC)-derived antibodies, leading to detection of specific antibodies in vivo-formed IC.