In any search for enteric carriers the patient with a positive blood-agglutination must be regarded as suspect. Earlier workers were of opinion that the converse of this was true—that a negative agglutination reaction implied that the case was not a carrier. It is true that McCowan and Mann (1925) described a series of nine carriers, of whom two showed a negative agglutination reaction during the clinical attack of typhoid fever, but the subsequent history of the agglutination reactions is not given. Ashby (1931) indicates in his series the prevailing belief that carriers show significant alterations in their agglutination reactions. Although repeatedly controverted in the medical literature by the publication of small groups of cases where the carrier state has been accompanied by negative blood-agglutination reactions, this view dies hard, and was revived during the recent discussions centring around the Croydon typhoid epidemic.