For the purpose of collecting information about cancer morbidity in the spouses of cancer patients treated during a ten‐year period, special questionnaires were sent to the physicians involved. Of 1,691 questionnaires, 898 were answered. Only tissue diagnoses by the physicians were accepted. According to th 898 returns, 40 spouses had cancer. Compared to the rate for new cases of cancer during the same period in New York State outside New York City (2,846 per 100,000), this was a rate of 4,454 per 100,000. The difference was statistically significant beyond .005. It is postulated that an additional endogenous factor in cancer patients, possibly an infectious one, may account for the increased incidence of cancer in the spouses of cancer patients in the present study. Further investigation is required, however.