The discovery of multiple polypi in a small child does not necessarily indicate that this is a case of familial adenomatosis. Two cases of juvenile polyposis were confirmed by histological examinations, and their clinical and, more particularly, their radiological characteristics were studied. The only way to explore the full extent of the lesions in a satisfactory manner is by double-contrast examination of the whole colon. The authors stress the value of radiological examinations, though the frequency with which they should be carried out is open to discussion. Review of the published literature reveals that the association of true familial polyposis or adenocarcinomatosis exists in the same family or even in the same patient. Diagnostic difficulties are usually due to the fortuitons co-existence of a lymphoid hyperplasia, the significance of which is still not known.