Histones are a group of similar, small, highly conserved nuclear proteins that bind to DNA by their many basic residues. The histones are divided into fractions, with each fraction having a distinct amino acid composition and sequence. Histones are also classified by relatively high levels of lysine and arginine. The presence of autoantibodies to histones are frequently found in several rheumatic disorders (1). In one study, the predominant responses to histones in SLE sera were to H1, H2b, and H3. Marked elevations of binding occurred to H1 and H2b in 33% of patients, while 25% showed higher binding to H3 (2). The same study showed the highest anti-histone reactivity to be in patients with rheumatoid arthritis with vasculitis, while the highest reactivity in SLE sera was in those patients with a history of photosensitivity (3).