Sera from 21 rheumatoid arthritis patients with accompanying neutropenia (less than or equal to 2000 neutrophils/microliter) and 45 rheumatoid arthritis patients without neutropenia were studied for the occurrence of IgD granulocyte-specific antinuclear antibodies. Such antibodies were found in 67 per cent of the neutropenic and 18 per cent of the non-neutropenic cases (p less than 0.001). The titres of IgD granulocyte-specific antinuclear antibodies varied independently of the titres of IgD and complement-fixing granulocyte-specific antinuclear antibodies, but showed some covariation with granulocyte-specific antinuclear antibodies of the IgA and IgM classes most probably reflecting a broad polyclonal antibody response to phagocyte nuclear antigens in the serologically highly active neutropenic cases. Gel filtration studies on selected sera containing IgD granulocyte-specific antinuclear antibodies indicated participation of these antibodies in immune complexes. It is thus possible that IgD granulocyte-specific antinuclear antibodies may have some significance for the rheumatoid inflammatory processes.