The specificity of antinuclear autoantibodies in a patient with a sensory neuropathy associated with cancer has been analyzed. The autoantibodies recognize the histone H10 as shown by its dissociation from DNA, perchloric solubility, electrophoretic mobility in SDS or urea/acid polyacrylamide gels, and by the capacity of purified H10 to block the reactivity of these autoantibodies. Almost no reactivity was observed with other subtypes of H1. To our knowledge, this is the first autoantibody described with such specific reactivity for the H10 subtype. © 1987.