Flow cytometric DNA analysis was performed in 67 tubular, tubulovilous and villous rectal adenomas with different degree of dysplasia. One of the adenomas contained a focus of early invasive carcinoma. All but one of the 67 adenomas had near diploid DNA histograms; the exception was a tubular adenoma with severe dysplasia but without signs of early invasion. Flow cytometric DNA analyses of adenomas may in some cases provide valuable information. The low frequency of aneuploidy indicates, however, that routine DNA measurements are questionable. Rather, the analysis should be restricted to certain cases like those with high malignant potential, cases with suspected early invasive carcinoma, and adenomas not radically removed.