The ‘G’ kindred is remarkable for the high incidence of a specific cancer aggregate in its members, particularly adenocarcinoma of the colon and endometrium, with relatively early ages of onset and a remarkably high incidence of multiple primaries. This specific familial association has previously been detailed in the literature as the ‘cancer family syndrome’. The parent-child concordance, observed between cancer-affected parents in the kindred and their 219 offspring, is 36.5%. The sibling-pair concordance for cancer, between first-affected siblings and their brothers and sisters, is 36.6% of 153 pairs. Manifestation of the familial malignancy in this particular kindred does not show sex influence, sex limitation, or disparity between matriarchal and patriarchal association for the cancer diathesis. The data are consistent with the hypothesis that the familial diathesis for the defined aggregate, in the ‘G’ kindred, is transmitted according to the mode of an autosomal domiant gene with an observed penetrance of about 73%.