The authors studied the effects of pupillary constriction (pilocarpine 2%) on automated static threshold perimetry in 20 normal subjects using the Humphrey Field Analyzer 30-2 and STATPAC programs. The mean defect (MD) worsened by an average of 0.67 decibels (dB) (standard deviation, 0.67 dB) in constricted fields compared with baseline visual fields (P less than or equal to 0.001). Independent comparisons of the unweighted means of threshold values for the central 30 degrees, 24 degrees, and 10 degrees were also done and showed significant reductions in sensitivity after constriction (P less than or equal to 0.001). These findings indicate that changes in pupillary diameter may produce significant declines in threshold sensitivities and support the importance of consistent pupillary diameters on serial automated visual field examinations.