BACKGROUND: Cancer affects patients' incomes, but to the authors' knowledge few studies to date have examined how the income of the patients' spouses may be influenced. In this population-based study from Norway, the effects of cancer on both partners' earnings are analyzed. METHODS: The difference between labor earnings the year before the cancer diagnosis and that 2, 5, or 8 years later was compared with the difference in earnings over a corresponding period for similar persons without cancer, applying linear regression models to national registry data. Approximately 1.1 million married persons ages 35 to 59 years were included, among them 17,250 persons diagnosed with cancer during 1991 through 1999. RESULTS: Two and 5 years after a cancer diagnosis, married men experienced lower earnings than they would have absent the illness. Cancer in wives, however, did not affect men's earnings. Women's earnings were adversely influenced to the same extent by their own as by their spouses' cancer. Brain, lung, and colorectal cancer in male spouses produced the most adverse effects on women's earnings. All effects were most pronounced for women no longer married. CONCLUSIONS: Women's earnings are lower after both their own and their spouses' cancer illness, and divorced and widowed women experience the most pronounced reduction after spousal cancer. Men's earnings are lower only if they are diagnosed themselves. This may reflect traditional sex roles, with men as main breadwinners and women as caregivers. For family households, cancer in men may result in greater financial difficulties than cancer among women, although the effect will depend on breadwinner roles before diagnosis.