The present study analyzed the development of manual midline crossing in a sample of one hundred sixty 2- to 6-year-old children and considered test construction factors that could affect the test design. The test construction factors addressed were (a) the effect of biasing the hand used for object manipulation and (b) the effect of distance from midline required for task completion on the frequency of manual midline crossing. A pegboard task was used to measure manual midline crossing. The results identified a developmental age trend in crossing the body midline in 2- to 6-year-old children. Biasing the hand used for object manipulation significantly increased the probability of eliciting manual midline crossing. A combination of linear and quadratic trends was found when the effect of distance from midline on the frequency of contralateral responses produced during testing was analyzed.