We determined HLA-A, -B, -C and -DR antigens in 83 patients with rheumatoid arthritis (RA) and reactive secondary amyloidosis (RSA), 60 in Finland and 23 in Poland, and compared the results with control RA patients and blood donors. There were no significant differences in the frequencies of HLA between the RA patients with and those without RSA in either Finland or Poland, and no significant differences between the Finnish and Polish patients with RSA. All the RSA patients from Finland and 70% of the RSA patients from Poland were seropositive. In the development of RSA, the prolonged period of inflammatory stimuli may play a more important role than genetic factors.