In this work we explore the possibility of designing a new iterative learning control scheme for systems without a priori knowledge of the control direction. By incorporating a Nussbaum-type function, a new learning control mechanism is constructed with both differential and difference updating laws. The new learning control mechanism can warrant a L-T(2) convergence of the tracking error sequence along the iteration axis, in the presence of time-varying parametric uncertainties and local Lipschitz nonlinearities. (C) 2004 Elsevier Ltd. All rights reserved.