Stored serum specimens collected in connection with a community‐oriented epidemiologic study were available from 30 subjects who later developed seropositive rheumatoid arthritis. In 9 of these pre‐rheumatoid specimens, the Rose‐Waaler test result was positive, and in 16, the latex fixation test was positive. Two‐thirds of the samples were positive when the interval between taking the blood specimen and onset of the disease was <4 years, and one‐third were positive when the interval was ≧4 years. The occurrence of rheumatoid factor preceded the onset of clinical disease more often in males than in females.