The purpose of this study was to investigate the validity of two-dimensional (2-D) analysis with respect to three-dimensional (3-D) analysis for recording rearfoot motion during walking. The results of this study indicated that rearfoot motion measured with either 2-D or 3-D analysis is essentially the same for the initial 60% of the stance phase. There was no significant difference between the two methods on variables typically measured in studies dealing with rearfoot motion. RELEVANCE: The assessment of rearfoot motion during walking in a clinical situation is frequently desirable yet the high cost of equipment and time required for 3-D analysis makes it unreasonable or impractical. The results of this study show that 2-D analysis can be used to measure rearfoot motion accurately and therefore is feasible for use in the clinic.