Abstract: The aim of this study was to examine the difference in serum immunoglobulin concentrations in the sera of rheumatoid arthritis (RA) patients, RA patients with acute myeloid leukaemia (AML) and to compare with those found in normal subjects. This study was performed in 43 of normal adult individuals (group 1), 40 RA patients (group 2) and 37 RA individuals with AML (group 3) were used for analysis of immunoglobulin levels by SDS polyacrylamide gel electrophoresis and ELISA. Measurements were made before treatment in the group with AML as well as when patients were both on and off chemotherapy. It was found that group 1 had a mean IgA level of 3.0 mg mL-1 and IgM level of 1.82 mg mL-1. Group 2 had a mean IgA level of 5.5 mg mL-1 and IgM level of 1.91 mg mL-1, while group 3 had a mean IgA level of 1.2 mg mL-1 and IgM level of 0.95 mg mL-1. Significant increases in IgA level in group 2 (p<0.00001) while the levels of both IgA and IgM in group 3 were significantly decreased (p<0.00001). This decrease was significant during induction and maintenance treatment, with restoration to normal once the patient was off therapy. There was no significant difference in IgG level in both groups 2 and 3 compared to group 1 (p<0.53). The finding of normal IgG level at diagnosis suggests that the leukaemia process itself did not initiate the fall. In addition, the influence course of treatment on rheumatoid arthritis patients with AML has a direct relation to the level of IgA and IgM due to complex interactions of chemotherapy.