In the present experiments the author studied the influences of four alkylphosphates such as parathion, diazinon, chlorthion and sumicide on serum protein, hematcrit value and hemoglobin content in blood of rabits and obtained the following: 1. Changes occurring when exposed to these alkylphosphates are common; namly, an increase in serum total protein, hematcrit value and hemoglobin content in blood as well as an increase in the A/G ratio, and a decrease in γ-globulin. 2. These changes reach the maximum at the peak of symptoms, namly, at the stage where serum cholinesterase is at the lowest level. Consequently changes occur differently according to the method of administration, for instance, the method in which the appearance of symptoms i...