The present paper is devoted to studying, with the aid of different organic dyes, the transmittance spectra of hemoglobin and immunoglobulin G extracted from the blood of laboratory rats, which have been chronically intoxicated with ethanol. The differences in the spectra are detected, when compare with those for the control group. It is shown that the presence of ethanol in blood probably leads to uncoiling partially the hemoglobin molecules. The essential difference is also found in the transmission spectra of immunoglobulin-dye solution prepared from the blood of the control-group animals and those of the animals of the first generation. The IgG of blood plasma of the first-generation rats probably includes a larger quantity of free remains, which could couple with the intoxicated agents. The small difference between the IgG-dye solution spectra for the animals given to drink ethanol during 6 months and the control-group animals is quite possibly referred to decreasing the IgG concentration after a durable ethanol intake.