Under a Phase I grant from the National Institutes of Health (NIH) Eunice Kennedy Shriver National Institute of Child Health and Human Development, Barron Associates has developed custom sensors, electronics, and software that enable a commercial glove orthosis, the SaeboGlove, to be used by stroke patients in conjunction with the SaeboVR software to practice activities of daily living involving manual interactions with virtual objects. A completed experimental study investigated the criterion validity of motor performance measures automatically derived from sensor data. Fifteen hemiparetic stroke patients completed four SaeboVR practice sessions of approximately one hour in duration. In the final session, patients additionally completed a battery of gold-standard assessments of UE motor function. Statistical analysis revealed strong and significant relationships between virtual world-derived measures and the gold-standard instruments, confirming the validity of the system for measuring upper extremity motor performance in stroke patients.