1. Findings concerning mental illness in husbands and wives are reported from two total population surveys carried out in the same region of southern Sweden in 1947 and 1957. All the survivors of the 1947 study were reinterviewed at the later date, irrespective of domicile.
2. In 1957 a highly significant excess of couples in which both partners were considered to be ill (at any time since the marriage) was found. The excess in number of concordant pairs was uninfluenced by age. Upper and middle social class couples showed an excess of conjoint illness very clearly, but none was found for those in the lower social class.
3. There were 269 couples who were seen in both surveys. In 1947 these couples had no tendency to conjoint illness, but by 1957 they showed a highly significant (p<.001) excess over the number to be expected, given the proportions of sick husbands and sick wives.
4. There was a general tendency for the wives of sick husbands to show a progressive increase in morbidity with increasing duration of marriage.
5. Chronicity of illness in the husbands could not be shown to influence the morbidity of wives, but the dating of the onset of illness was often very uncertain. On the other hand, remission of illness in the husband was clearly related to lower illness rates in the wives, except in the lowest social class.
6. Diagnostic data are presented, but these did not warrant detailed analysis. Significant correlations on personality dimensions, using Sjöbring's system, were found for two of four dimensions among healthy pairs, on one dimension when the husband was well but the wife ill, and on none in the remaining categories.
7. Methodological points are briefly considered. Attention is drawn to the special situation of lower class wives. The contribution of duration of marriage and chronicity of illness are reviewed in conjunction with findings from the literature.
8. A statistical Appendix demonstrates that the risk of a healthy wife becoming ill if her husband is ill is significantly greater than that for the healthy husband of a sick wife.