The rate of destruction of calcified schistosome eggs in host tissues is a matter of fundamental concern for the interpretation of the number of eggs found in the tissues of infected persons. Smith and von Lichtenberg recently presented interesting and unexpected results after injecting calcified eggs from a human bladder intravenously into mice (Am. J. Trop. Med. Hyg., 25: 595–601, 1976). They note that “calcific eggs, which elicit no cellular response in their human host, can incite a granulomatous response when transferred to another host, the mouse.” This conclusion, amply supported by the results, suggests that removal of the eggs from the sandy patch in the human bladder radically altered the ability of the host to react to the eggs. One cannot then conclude that the destruction of these dispersed eggs by the mouse has any bearing on the fate of calcified eggs in the sandy patch in the human bladder, and the comparison made of egg destruction in man and mouse is not justified.