A modification of the Dale, Curley, and Cueto method for the determination of p,p'-DDT and p,p'-DDE in whole blood is described. It offers the advantages of rapidity and simplicity over the original method in the laboratory analysis of a large number of blood samples. Reproducibility and percentage recovery of the organochlorine pesticide residues were found entirely satisfactory. The modification was comparable, (r) = 0.92, to the original method when used with whole blood. Plasma and whole blood values of DDT and DDE were found to be unrelated to actual hematocrit corrections when readings were between 40 percent and 54 percent. It is speculated that this would not be true with blood specimens exhibiting high degrees of hemoconcentration or hemodilution. The correlation of both DDT and DDE concentrations in plasma with those in whole blood was (r) = 0.91 when the hematocrit was assumed to be 50 percent.