A total of 343 dogs were administered perorally with 5 and 10 mg/kg of diethylcarbamazine preparation. Of them, seven (2.0%) manifested transient salivation and vomiting and six (1.7%) fell in severe shock soon after medication on account of central nervous system involvement and died. The six dogs attacked by shock were found to have harbored Filaria larvae in the blood. (They were 4.9% of 123 dogs infected with filariasis.) They exhibited the same clinical signs as the clinical case of

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... sis. From these results, it was confirmed that the administration of this preparation induced severe shock in dogs when filariae had infected them, and caused death eventually. It is presumed that the shock might result from allergy to that drug. Under these circumstances, that drug can be used for the prevention of canine filariasis only in uninfected immature dogs in which it is proved to have no larvae in the blood. When it is given its daily dose should be 11 to 22 mg/kg.