Postural stability is an important component of skilled athletic activity. However, the effects of foot orthoses on stability have not been adequately addressed. This study measured postural sway in 30 asymptomatic professional soccer players in three standing positions and four underfoot conditions. The results revealed that the underfoot condition had no significant effect on sway in the mediolateral or anteroposterior planes; however, there was a trend toward less mediolateral sway when subjects stood in a unipedal position with prefabricated orthoses. These results suggest that insoles and foot orthoses have no significant beneficial or detrimental effects on postural stability in asymptomatic subjects. Clinically, this suggests that no improvements in balance performance could be expected with prophylactic use of insoles or orthoses but that clinicians may prescribe insoles and foot orthoses without fear of impairing postural performance in elite athletes.