The study analyses the expression of DNA-ploidy, ki-67, PCNA and p-53 and their role as potential markers of the development of colorectal adenomas. METHODS: 34 adenomas of the large intestine were analysed using endoscopic exeresis in 15 males and 13 females with a mean age of 64 years (range 42-80). Flow cytometric analysis was carried out to calculate the DNA-index and immunohistochemical tests were used to evaluate ki-67, PCNA and p-53. Statistical analysis was based on chi 2 test and Student's "t"-test. RESULTS: The DNA index was not statistically correlated with the histotype and grading. Ki-67 was highly positive in 5 adenomas, 2 aneuploids and 3 diploids, but did not show a clear relationship with other growth parameters. On the contrary, p-53 was statistically correlated with the more advanced degenerative state of adenomas, being pathological in 6 cases (30%), all with marked aneuploidy (p < 0.02) and severe dysplasia (p < 0.004). PCNA, which was also pathological (> 40%) in 4 (23.5%) aneuploid adenomas with severe dysplasia (2 villous and 2 tubulo-villous), appeared to be significantly correlated with the DNA index (p < 0.005), showing a proliferative index of exceptional clinical importance. CONCLUSIONS: The results of this study show that p-53 and PCNA are two parameters that contribute to the definition of the degenerative risk and allow patients to be selected for constant monitoring, although additional follow-up data are essential to enable the clinical verification of these results.