The prevalence of rheumatoid arthritis, rheumatoid factor, antinuclear autoantibodies, thyroglobulin and thyroid `microsomal' autoantibodies and gastric parietal cell autoantibodies has been studied in 327 husbands and 181 wives of 508 probands with seropositive `definite' or `classical' rheumatoid arthritis as defined by the American Rheumatism Association diagnostic criteria. Two husbands and three wives had definite rheumatoid arthritis: this prevalence is no higher than one might expect. A higher prevalence of all five autoantibodies was found in husbands compared with age matched controls, but only in respect of antinuclear autoantibodies and thyroglobulin autoantibody were the differences statistically significant. In the wives only rheumatoid factor showed a significantly higher prevalence as compared with controls. The presence of autoantibodies in husbands and wives showed no relationship to the duration of marital contact nor to the presence of the autoantibodies in the probands. The prevalence of autoantibodies in spouses of probands who developed their arthritis after marriage showed no difference when compared with that in probands who developed their arthritis before marriage.