Abstract
Extracts of human colonic adenocarcinomata were made with perchloric acid and shown to contain antigens which were not present in pooled samples of normal colonic mucosa or in healthy colonic mucosa from patients providing the tumours. Antisera prepared against the tumour extracts gave two precipitin lines on immunodiffusion, and antiserum prepared in Montreal according to the methods devised by Gold and Freedman (1965a and b) also gave two lines of precipitation when tested against some of these extracts; one of these precipitin lines gave a reaction of identity with that given by the antiserum produced here. The results suggest that perchloric acid may extract two antigens from colonic carcinomata.