Commonly used modifications of the Dukes'' system for staging carcinomas of the [human] colon and rectum are inaccurately presented in many current textbooks and articles. These modifications divide Dukes'' Stage B category into B1 and B2, depending on whether or not the lesions has invaded or penetrated the muscularis propria. The term muscularis propria has been incorrectly interpreted to mean muscularis mucosa, as a result A, B1 and B2 lesions, according to the modified systems, all correspond to Dukes'' Stage A category, and there is no modified stage corresponding to Dukes'' Stage B. The term modified Dukes should be discarded and modified systems should be given the eponyms of their describers. If the modified systems are to be continued, they must be correctly understood and presented. The simple and unambiguous nature of the original Dukes'' system favors its widespread use.