We present findings on plasma CEA in relatives and spouses from six kindreds manifesting the Cancer Family syndrome. The CEA distributions per se were transformed to square root CEA to correct for skewness and kurtosis. Significant effects of age and duration of smoking were adjusted for by linear regression. Relatives were classified as: 1) cancer patients, 2) individuals at high genetic cancer risk (one or more first-degree relatives affected, and 3) individuals at low genetic cancer risk (no first-degree relatives affected) for statistical comparisons. Unrelated spouses were also classified into corresponding groups according to their directline mate's status. Cancer patients and relatives at high genetic risk had significantly greater mean square root CEA than relatives at low genetic risk, and, surprisingly, unrelated spouses had mean levels of square root CEA which were similar to that in the corresponding cancer risk class of their direct-line mates. Our results suggest the existence of both a genetic and connubial effect on CEA, presumably due to a common environmental agent acting in concert with the degree of genetic predisposition to oncogenesis in this syndrome.