Abstract: The aim of this study was to investigate the presence of anti-immunoglobulin antibodies in patients with rheumatoid arthritis, using as a target goat immunoglobulins, in an attempt to elucidate further complex immuno-pathogenetic interactions of the disease. Serum immunoglobulin A concentrations were measured by ELISA technique in twenty patients with rheumatoid arthritis and twenty matched normal adult individuals. The effect of anti-goat immunoglobulin antibodies leads to an overestimation of serum IgA level in patients; this increase is different for each sample estimated by ELISA. Visualization of IgA by immunoblotting technique confirms that goat immunoglobulins were co-precipitated with the antibody-antigen complex. Initial results before purification from the interfering anti-goat immunoglobulin antibodies suggested that patients had increment levels of IgA in their sera. It was found that normal individuals had a mean IgA level of 2.77 mg mL^-1 and patients had a mean IgA level of 5.13 mg mL^-1 (p<0.00004). While, the mean level of IgA in patients after purification from anti-goat immunoglobulins was 2.92 mg mL^-1. Therefore, there was no significant difference in IgA level in patients purified from anti-goat immunoglobulin antibodies compared to normal individuals (p<0.33). A circulating immunoglobulin reacting with other immunoglobulins is thus present in patients with rheumatoid arthritis and may well play a part in the complex immuno pathogenetic interactions.