In this note, we present a general input-output approach that can be used for the design and analysis of robust discrete-time adaptive control schemes. In particular, we consider a model reference adaptive controller. The design approach involves the use of the Certainty Equivalence Principle to combine a robust control structure with a robust adaptive law. Using exponentially weighted l2 norms and exploiting the properties of the adaptive law and the control structure, robust stability is established for the closed loop adaptive control scheme. For clarity of presentation, the analysis is kept qualitative, though necessary modifications are indicated for obtaining a quantitative result.