OBJECTIVES. Visual disorders among preschool-aged children are common, yet screening is infrequent. The purpose of this project was to implement the vision screening recommendations proposed by the Maternal and Child Health Bureau and National Eye Institute Vision Screening in the Preschool Child Task Force: monocular visual acuity and stereopsis testing. METHODS. Four sites fully participated in the implementation of the task force recommendations with 3- and 4-year-old children. Two of the sites worked with primary care practices (testing performed by staff); 2 worked with community-based programs (testing performed by lay volunteers). Each site tracked number of children screened by age, as well as proportion testable, referred, and with documented follow-up evaluation. RESULTS. Variations in implementation of the recommendations were observed. Successful screening among 3-year-olds ranged from 70% to 93%; referral rates were 1% to 41%, and follow-up rates were 29% to 100%. Successful screening among 4-year-olds ranged from 88% to 98%; referral rates were 2% to 40%, and follow-up rates were 41% to 100%. The proportion of 3-year-olds who were treated was significantly different between the community-based sites (n = 20) and the primary care sites (n = 2). Similarly, the proportion of 4-year-olds who were treated was significantly different between the community-based sites (n = 36) and the primary care sites (n = 11). CONCLUSIONS. The variability across pilot sites in numbers successfully screened and numbers referred suggests that all aspects of preschool vision screening need thorough review before the goal of universal preschool vision screening can be realized. Copyright © 2006 by the American Academy of Pediatrics.