This paper presents a Variable Structure Adaptive Backstepping Controller (VS-ABC) for plants with relative degree one, using only input/output measurements. Instead of traditional integral adaptive laws for estimating the plant parameters, switching laws are used to increase robustness to parametric uncertainties and disturbances, as well as, to improve transient response. Moreover, the controller design is easier when compared with the original adaptive backstepping controller, since the amplitude relays are related to the plant nominal parameters. Additionally, preliminary simulation results for an unstable second order system are shown.