Development of colorectal neoplasia in a patient subject or predisposed to colorectal neoplasia is reduced by the steps of (a) determining a patient is subject or predisposed to colorectal neoplasia; and (b) enterically delivering into the gut of the person an effective amount of an aminoglycoside antibiotic having poor gut absorption, whereby the development of the colorectal neoplasia is reduced as compared with otherwise similar non-treated patients.