In May, 1956, several analyses of the atmospheric benzene concentration in spray-painting factories of motor-cars and general examinations were made on 16 workers exposed to thinner (benzene) during their working hours, and the following results were obtained. 1. The atmospheric benzene concentration in each plant was 15-96 p.p.m. at the breathing level of the laborers working at about 1 meter away from the sprayer and the concentration was about 67 p.p.m. on the average. 2. Blood examinations: An increase in the hemoglobin content was not observable, but a decrease in the red cell count was seen with a tendency towards an increase in the average diameter of the cell, and red cells indicated a picture of macrocytic-hyperchromatic anemia. A decrease in the leucocyte count was obvious, especially, neutrophil leucocytes showed the decrease in both relative percentage and absolute counts and also the leftward nuclear shift was recognized. 3. Some workers complained of fatigue, loss of bodyweight, dizziness and sleeplessness as the subjective symptoms. 4. Ethereal sulfate ratio and conjugated phenol ratio in the urine exhibited a considerable increase both before and after the work as compared with those of the control.