In this retrospective study a comparison was made between the disease manifestations in patients with isolated elevation of IgA rheumatoid factor (RF) and patients with elevation of IgM RF. Of the 28 patients with isolated elevation of IgA RF, 14 (50%) had rheumatoid arthritis (RA) and 9 (32%) miscellaneous other inflammatory rheumatic disorders. It was found that 61% of these 23 rheumatic patients had disease manifestations from mucous membranes or secretory organs compared to 18% in the IgM RF positive group (p = 0.020). Patients with RA and an isolated elevation of IgA RF had more often mucosal or secretory symptoms than RA patients with elevation of IgM RF. We suggest that IgA RF may be a marker for activation of the mucosal or secretory immune system. The relationship between IgA RF and non-articular symptoms is discussed.