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A comparative study of colorectal adenocarcinoma was undertaken among the populations of Jordan and Nova Scotia, Canada. The incidence of this cancer was 13 (colon 6, rectum 7) and 53 (colon 31, rectum 22) per 100,000 males aged 35--64 years, respectively. Colonic tumors (excluding rectosigmoid) showed left-sided preponderance in Jordanians and right-sided preponderance in Nova Scotians. Age average at diagnosis was 49 years in Jordanians (colon 47 years and rectum 50 years) and 66 years in Nova Scotians (colon 67 years and rectum 63 years), with peaks in the fifth and seventh decades and a male to female ratio of 1.3:1 and 1:1, respectively. The mucinous type accounted for 31 and 13% of colorectal adenocarcinomas in Jordanians and Nova Scotians, respectively, of which the signet-cell type accounted for 14 and 2% of the total number, respectively. The actual incidence rate of mucinous carcinoma, however, was higher among Nova Scotians. In both groups, mucinous carcinoma showed predilection for females and rectal signet-cell carcinoma showed bias toward younger females. The authors believe that the significantly different epidemiologic and morphologic features of colorectal cancer demonstrated in these two communities could shed light on possible etiologic influences, such as dietary habits or other environmental factors.