The relationship between pupil size and perimetric sensitivity was investigated in group of clinically normal emmetropic subjects using the Dicon AP3000 computer‐assisted perimeter at bowl luminances of 10 asb and 45 asb. Pupil size was modified with the motic thymoxamine 0.5% and the mydriatic phenylephrine 10%; saline was used as the control. Perimetric sensitivity increased with an increase in pupil size. The effect was greatest for peripheral locations for both bowl luminances. The fluctuations in perimetric sensitivity increased with peripheral angle and with decrease in pupil size for both bowl luminance