In order to evaluate the representativeness of a monitoring station for nitrogen dioxide in an urban area of Okayama City, the nitrogen dioxide concentration was measured in the area six times between 1982 and 1984. The area was divided into 96 sections and the concentration of nitrogen dioxide was measured at the central part of each section and at a continuous monitoring station located in the area. From the measured values, the distribution of nitrogen dioxide concentration levels was determined and the correlation coefficients of the levels at the measuring points were calculated. The results show that the nitrogen dioxide concentration levels vary according to the direction and strength of wind, and other factors, but the levels of nitrogen dioxide at the continuous monitoring station were close to the mean level of the 96 measuring points throughout all observation days. The correlation coefficients between the nitrogen dioxide levels at the continuous monitoring station and those of the other 96 measuring points were large. It can be concluded that the present continuous monitoring station is one of the best points to monitor nitrogen dioxide concentration in the urban area of Okayama City.