BACKGROUND The Randot Preschool Stereoacuity Test is a widely used three-book test for the assessment of binocular status. Using a prototype, we previously reported high testability in children as young as 3 years, validity data, and some normative data. Here we report extensive normative and validity data for the final version of the test. In addition, we report normative data for a new, fourth book that adds finer disparities. METHODS The Randot Preschool Stereoacuity Test was administered to 4355 normal children aged 3 to 18 years and 39 adults in multiple settings. In addition, the Randot Preschool Stereoacuity Test along with the new, fourth book that added 30 arcsec and 20 arcsec disparity levels was administered to 1402 normal children aged 3 to 18 years and 33 normal adults. Both the four-book Randot((R)) Preschool Stereoacuity Test and the Randot circles were administered to 242 patients with amblyogenic conditions aged 3 to 18 years. RESULTS Mean normal stereoacuity improved from 100 arcsec at 3 years of age to 60 arcsec by 5 years and 40 arcsec by 7 years. The lower limit of normal was 400 arcsec at 3 years, 200 arcsec at 4 years, and 60 arcsec at 7 years. Using the new four-book version, further improvement in mean stereoacuity could be appreciated beyond 7 years of age to 30 arcsec in the 11- to 18-year-old and adult groups. Among the 242 patients, Randot Preschool Stereoacuity Test stereoacuity was strongly associated with Randot circle stereoacuity (chi(2) = 261.0, p < 0.001). CONCLUSIONS Normative data for the Randot Preschool Stereoacuity Test show a monotonic improvement of stereoacuity from age 3 years through the teen years. Patient data support the validity of the Randot Preschool Stereoacuity Test.