An adaptive version of the twisting algorithm is proposed, which actually presents a new second-order sliding-mode algorithm. Due to the dynamic adaptation of the gains the con- troller design does not require complete information on the bounds of uncertainties and perturbations. It automatically decreases the gains and respectively also the dangerous os- cillations due to a too large discontinuous-control magnitude. Thus, both the performance and the accuracy of the closed-loop system are improved. In order to show the feasibil- ity of the approach, the methodology is successfully applied to control the position of a pneumatic actuator in an experimental setup.