This study was undertaken to determine whether the rheumatoid factor (RF) isotypes affect the level of IgA-AT complex in early rheumatoid arthritis. IgA-AT complex and IgM, IgG, and IgA RF were evaluated using a double antibody enzyme-linked immunosorbent assay (ELISA) in sera of 83 (61 women and 22 men) patients. The mean level of the complex was higher in RA patients as compared with the control group (0.60 +/- 0.41 U vs 0.19 +/- 0.11 U, p < 0.05). The IgA-AT complex values exceeding the norm were found in 19 of 83 RA cases (23%), mainly in patients non-treated with DMARDs. IgM RF values judged as positive were present in 53 (64%), IgG RF in 55 (66%), and IgA RF in 56 (67%) patients. Higher RF values of IgM and IgG, but not those of IgA class, were found more frequently in patients with elevated IgA-AT levels. A good correlation was established between IgA and IgM RF (r = 0.61, p < 0.01), but not between IgA and IgG, or IgM and IgG RF in the group of patients under study. However, we did not find any significant correlation between isotypes of RF and parameters of the disease activity.