The main object of this study was to see whether or not chromatin constituents are present in cell membranes. The binding of antinuclear antibodies (ANA) to plasma membranes of leucocytes was studied by using autoantibodies and induced antibodies to different histones and histone peptides, and autoantibodies to double-stranded DNA (dsDNA) in adsorption-elution experiments. Eluates were subsequently tested for antinuclear antibodies by a solid-phase ELISA. No ANA activities in the eluates were observed, except when true cross-reacting ANA were employed in the study. Furthermore, no binding of these antibodies to plasma membranes could be visualized by indirect membrane fluorescence tests. The conclusion of these studies was that freshly isolated viable leucocytes did not carry detectable amounts of ectopic chromatin components at the level of plasma membranes. Thus, it seems fairly unlikely that chromatin autoantibodies in general exert some tissue damage by binding to homologous nuclear antigens associated with plasma membranes in vivo.