OBJECTIVE: To establish the degree of modulating influence of the type of surfaces (whether stable or labile) on the dynamic balance responses during the sit-to-stand transfers in both stroke patients and healthy controls. METHOD: We evaluated sit-to-stand balance by Balance Master (NeuroCom, USA) in 30 hemiparetic patients and 10 healthy controls. All subjects were requested to perform sit-to-stand transfers three times each on the both stable and labile surfaces. Four balance indices (weight transfer time, rising index, COG sway velocity, left/right weight symmetry) were obtained. RESULTS: In hemiparetic patients, decreased rising index, increased COG sway velocity, increasing left/right weight asymmetry were noticed. During sit-to-stand transfers from sitting on labile surfaces to standing, rising index increased and left/right weight asymmetry increased in hemiparetic patients, but not in healthy controls. This implies that the maximum vertical force exerted by legs during the rise phase increased, but the differences of weight borne by each leg during the active rising phase increased in hemiparetic patients. CONCLUSION: Weight bearing exercise on the affected leg as well as strengthening exercise of legs are considered to be essential to decrease the falls during sit-to-stand transfer in stroke patients.