OBJECTIVE: Sasang constitutional medicine is a component of Traditional Korean Medicine that stresses the hereditary makeup of disease incidences or therapeutic responses. This study investigated the relationship between the incidence of cancer and Sasang constitution classification. METHODS: Five hundred and one cancer patients were classified as having one of the four types of Sasang constitutions (Taeumin, Soumin, Soyangin, Taeyangin) using Questionnaire for Sasang Constitution Classification II, then compared with data from 1423 healthy subjects. RESULTS: The Sasang constitutional distribution for the cancer patients was significantly differentfrom that for healthy subjects: 22.8% vs 46.9% for Taeumin, 35.5% vs 24.0% for Soumin, and 41.7% vs 29.1% for Soyangin. Our results assumed that the lowest cancer incidence would be in Taeumin (around 2-fold in both sex) while the highest cancer incidence in Soumin males (2.8-fold) and Soyangin females (2.1-fold). CONCLUSION: This study identified a trend involving the frequency of cancer and the Sasang constitutional classification. We hope that this finding will provide new ideas for the study of cancer incidence and its preventive management.