In the measurement of sulfur oxides in air by alkaline filter paper method, the effect of the concentration of the portassium carbonate solution in preparing alkaline filter papers on the values of sulfur oxides was studied. Any difference between the values obtained by the papers treated with 50% and 30% potassium carbonate solution was never found. Furthermore, the correlation between the values of sulfur oxides obtained by conductometric method and alkaline filter paper method was studied, and it was found that there was a good correlation between twomethods. The equation of regression curve was as follows ; Y=0.0334X+0.0083 (Y : the concentration (ppm) of sulfur oxides obtained by conductometric method, x : the values (mg SO3/day/100cm2) of sulfur oxides obtained by alkaline filter paper method, ) This equation was similar to Wilsdson's formula.