Patients with rheumatoid arthritis (RA), 500 males and 500 females, aged 40 years and over, together with an age- and sex-matched control population, were observed over a 10-year period. Altogether 208 male and 148 female RA patients died during the follow-up period. RA was mentioned on the death certificates of 111 men (53%) and for 96 women (65%). Serious underreporting of RA was observed when the main cause of death was malignant neoplasms and diseases of the circulatory system. The results show that analysis of the causes of death can be highly biased if the RA diagnosis is based only on information on the death certificate.