The purpose of this paper is to propose that the Contrastive Analysis Hypothesis (CAH) should be revised to incorporate a notion of degree of difficulty. This notion corresponds to typological markedness which can be determined independently of any particular language and independently of the facts concerning second language acquisition. Moreover, it is argued that if typological markedness is incorporated into the CAH, it is possible to predict not only the areas of difficulty for a second language learner, but also the relative degree of difficulty. Finally, it is argued that given certain assumptions about language and human learning, typological markedness is a natural and highly plausible notion of difficulty.