This is a long-term project (10 years or longer) set up together with the Department of Human Genetics. The answer to this question through genetics, epidemiological, clinical study has not been found despite the fact that some colonic diseases have a significant risk of malignancy. The project is at the phase of accumulating clinical and genetic material. All cases of juvenile polyposis coli have blood and polyps stocked for DNA study; in the meantime the classical hystological examination is performed. It would be interesting to succeed in organising a multicentre (international study), but this has not yet been realised