Background: Previous studies indicate that older adults, like young adults, can efficiently search for a briefly presented visual target defined by a single salient feature presented amidst background distractors. However, little is known about older adults' ability to identify the spatial location of targets during this aspect of preattentive processing. Objective: This study examined the extent to which older adults exhibit localization problems during feature search for a target with high conspicuity. Their performance was compared to that of younger adults. Methods: Twenty older adults (mean age 70 years, 8 men and 12 women) and 20 younger adults (mean age 25 years, 6 men and 14 women) with good central and peripheral vision were tested. Subjects were asked to indicate via a computerized touch-screen the location of a briefly presented (80 ms) target presented amidst distracting stimuli (set size 8, 16, or 32). Targets were presented at either 10°, 20°, or 30° eccentricity. The dependent measures were percent correct localization and, for trials in which there were errors, the spatial magnitude of the error. Results: Compared to young adults, older adults committed more localization errors during feature search, a problem which was accentuated with increasing target eccentricity. In addition, older adults' mislocalizations deviated from the correct location by greater distances. Conclusions: Older adults have spatial localization problems in preattentive processing during feature search, which could be detrimental to the guidance and deployment of visual attention. Copyright (C) 2000 S. Karger AG, Basel.