Cancer frequency has been studied in a Department of Crete and a Department of Sweden, using in-patient data collected in the Departmental Hospitals, for a two-year period. The results of the study suggest that similar trends exist in the prevalence of different forms of cancer between the two areas studied, as well as some significant differences. The differences observed concern mainly the frequency of cancers of the lung, prostate, bladder and large bowel among men and breast and large bowel among women. These findings could to a great extent be explained by life-style and environmental differences between the two areas and are consistent with data concerning the cancer mortality in the two countries.