The mucin histochemical and histologic features of 166 colorectal adenomatous polyps from 124 patients were studied. A majority of the polyps (62%) had a tubular growth pattern whereas 38% showed villous growth. Severe dysplasia was more frequently found in the latter group. A significant correlation (r = 0.27, P less than 0.001) was found between the severity of dysplasia and the size of the polyps. Moreover, the ratio between goblet and columnar cells was also found to decrease (P less than 0.0001) with the severity of dysplasia. Independent of the mucin stain used (periodic acid-Schiff, alcian blue, and high-iron diamine stains), mucin reactive cells were found to be negatively correlated (-0.17 less than r less than -0.44, P less than 0.01) with severity of dysplasia, especially in the tubular adenomas. These findings suggest that evaluation of mucin stain, related to dysplasia, may contribute to the assessment of premalignant and early malignant changes in adenomas of the colon.