The correlation between the histopathological diagnosis of biopsies from colorectal villous tumours and that of the excised tumour (in 16 cases of carcinoma only clinical diagnosis, autopsy or death certificate) was investigated. In the persent retrospective study 235 biopsies were taken from 134 tumours where the final diagnosis had been established. In the benign groups the grade of the biopsy was the same as that of the surgically excised tumour in about 50%. However, 25% of the biopsies with a benign diagnosis were in fact taken from carcinomas. Not even multiple biopsies exclude the presence of cancer in a villous papilloma. The tumour should be totally excised and histologically examined.