We present a hypothesis as to the cause of diverticulosis coli which is consistent with its geographical distribution, its recent emergence as a medicalproblem, and its changing incidence. Diverticulosis appears to be a deficiency disease caused by the refining of carbohydrates which entailsthe removal of vegetable fibre from the diet. Consequently we consider it to be preventable.

Diverticulitis first became a clinical problem at the turn of the century, and the term" diverticulosis" first appeared in 1914. As recently as 1916 the disease was not important enough to merit a mention in textbooks.'Though the present incidence of diverticulosis is unknown it is certainly endemic in our aged citizens. This dramatic increase in incidence occurred in only 70 years and cannot possibly be explained on a genetic basis. This changemight be due to observer error and be apparent rather than real, but we believe that their writings show that the clinicians of the last century were just as capable as those of today of recognizing diverti-culitis. We believe that there is another possibility-namely, that the colon's environment has changed and that diverticula are caused by the diet of so-called" civilized" countries.