Objective: To identify changes in sagittal- and frontal-plane center of pressure (COP) excursion length and velocity during single-leg stance under 6 orthotic conditions. Design: 1 3 6 repeated-measures. Setting: University biomechanics laboratory. Participants: Fifteen healthy young adults without excessive forefoot, arch, or rear-foot malalignments. Measurements: Selected variables of COP length and velocity were calculated in both the frontal and sagittal planes during three 5-second trials of quiet unilateral stance. Methods: Postural control was assessed under 6 conditions: shoe only and 5 orthotics. Results: The medially posted orthotic caused the least frontal COP length and velocity, and the Cramer Sprained Ankle Orthotic¨ caused the greatest frontal-plane sway. No significant differences were found between the different orthotic conditions in sagittal-plane measures. Conclusions: Differently posted rear-foot orthotics had various effects on frontal-plane postural control in healthy participants. Further research is needed on pathological populations.