Carcino embryonic antigens (CEA) or CEA-like antigens were explored in 61 perchloric extracts from stools or meconium. CEA was present in 8 out of 30 extracts in digestive cancers and in 6 out of the 31 other extracts studied. Two other constituents called NCA and NCA2 were frequently found. They were partially identical with CEA immunochemically. Owing to their frequency, they will be considered as normal constituents of the feces. Thus, characterization of CEA or CEA-like antigens in the stools by means of Ouchterlony’s double immunodiffusion does not seem to discriminate between cancerous and non-cancerous stools.