The latest Smartphone’s have built-in motion sensors called a tri-axis accelerometer. One of the clinical measures that can take advantage of this technology is balance assessment. Previous studies assessing balance show the need for familiarization. PURPOSE: The purpose of this study was to determine if a familiarization test was needed when using Smartphone devices to measure balance. METHODS: 49 healthy individuals (18 male, 31 female; 23.1±2.6 years) performed a bilateral, tandem, and single leg balance tests. A barefoot familiarization was recorded for the 3 stances, and then follow-up testing was done in barefoot, five-toed shoes, and athletic shoes. All trials consisted of 10-second measures with eyes closed and were random in order. A commercially available Smartphone was used to determine postural sway. One trial was completed for each test with an average of 4-minute rest between trials. RESULTS: Significant differences were demonstrated between familiarization and each of the assessments that followed (barefoot p=0.007; five-toed shoes p=0.023; athletic shoe p=0.028). No differences were observed between barefoot and five-toed shoes (p=0.576), barefoot and athletic shoes (p=0.521), or five-toed shoes and athletic shoes (p=0.901). CONCLUSION: Outcomes of this study show that balance data measured with a mobile device requires a familiarization trial. This is in agreement with previous publications using laboratory based balance assessment equipment and shows that familiarization is necessary when assessing balance regardless of equipment used. This may also suggest good consistency with Smartphone technology but should to be studied further.