Nitrogen dioxide and sulfur dioxide are two major air pollutants. As it has been well known, the former is one of major components of photochemical oxidants and the latter plays indispensible role in London type smog accident. In the field of industrial toxicology, these two noxious gases are classified as irritant gas physiologically and many reports on the acute and chronic intoxication by these two gases have been filed. A strong irritating effect of these two gases on the epithelium of air way tract and the formation of methemoglobin by nitrogen dioxide has been ascertained as main toxic actions of these gases. Author designed this study to evaluate the value of hemogram, organ water contens and organ-body weight ratio as the quantitative indices for the physiological & pathological changes induced by the exposure to 100ppm, 500ppm & 1,000ppm of NO₂ & SO₂ gases for 4 hours. Following findings were observed : 1) In the NO₂ exposure group, increase in the hemoglobin & hematocrit values was found and the degree of changes was proportional to the concentration of NO₂ but the number of leucocytes was reduced. In the SO₂ exposure group, a reduction of hemoglobin & hematocrit values was found and the degree of the changes was inversely proportional to the concentration of SO₂ Leucopenia was found as in the NO₂ exposure. 2) In the NO₂ exposure group, water contents of the lungs and brain were increased and the reduction was found in the adrenal glands. The degree of changes were remarkable in the lungs and proportional to the concentration of NO₂. In the SO₂ exposure group, same trends were found as in the NO₂ exposure except the brain which showed no changes. The degree of the changes were dominant in the NO₂ exposure group than that of the SO₂ exposure group. 3) Organ-body weight ratio was increased in the brain, lung, and heart in the NO₂ exposure group and in the SO₂ exposure group, the increase was observed in the lung alone and the reduction was found in the adrenal glands. The degree of the changes was proportional to the concentration in both NO₂ & SO₂ exposure groups.