A study was made on the error resulting from the measurement of the different fractionation of serum protein by the electrophoresis method. The error was studied on two groups: one group consisted of measurements made by many people on one sample (I), and the other consisted of measurements made repeatedly on the same sample by one person (II). Results obtained were as follows:
1) The standard deviations of the group consisting of many people, including several untrained, for albumin, α-globulin, β-globulin, γ1-globulin and γ2-globulin were ±4.2%, ±2.6%, ±4.4%, ±2.4% and ±2.2% respectively.
2) The causes of the deviations were unsatisfactory separation of the various peaks, β-disturbance and unskillful tracing of the pattern by the untrained.
3) The deviations of the measurements made by one person on the same sample, group II, for albumin, β-globulin and γ1-globulin were markedly smaller than in the group I.
