The density of mucosal lymphoid follicles has been determined in the large intestines of five sudden death victims. The specimens were fixed in acetic acid which made the follicles visible macroscopically. The estimated total number of follicles in the large intestine ranged from 12761 to 18432. The average density of follicles was 18.4 per cm2 in the caecum, 15.0 per cm2 in the colon and 25.4 per cm2 in the rectum. These results indicate that the density of lymphoid follicles has been grossly underestimated in the past where three to five follicles per cm2 have been accepted as normal. The cause for this major discrepancy is discussed as is its bearing on the diagnosis of lymphoid hyperplasia.