Schachter (1974) drew attention to the importance, in error analysis, of examining not only the L2 forms actually produced by the learners of a foreign language in their attempts to express themselves in L2, but also the L2 forms they seem consistently to avoid using. She also noted the close interrelation between such avoidance phenomena and the Contrastive Analysis approach to L2 teaching and learning: avoidance is the reverse side of negative transfer, since learners tend to avoid using in L2 those structures that have no parallel in their L1 and therefore provide them with no pattern for transfer. Of course, as Kleinmann (1977) has pointed out, “avoidance” implies that the structure in question is known to (i.e., can be passively recognized by) the learners, but not freely used by them; failure to use a structure or word that is unknown to the learners is an indication merely of ignorance, not of learning difficulty. Now a prime constructive purpose of error analysis is (or should be) to identify the sources of a learner's difficulties, as a necessary preliminary to helping him or her overcome them. Hence the importance of genuine avoidance phenomena that, when properly identified, can throw light on what would otherwise remain hidden recesses of uncertainty in the learner's mind. Levenston (1971) has convincingly argued, with numerous illustrations, that avoidance (“under-representation” in his terminology) of various English “clause (or group) structures” by Hebrew-speaking learners of English can be explained by the lack of Hebrew “translation-equivalents” for the English structures in question and the learners' consequent choice of less appropriate but more L1-equivalent structures. However, since Levenston was concerned not with avoidance phenomena as such, but rather with the evidence they provide of L1 interference with L2 learning and their stylistic effect on the learner's L2, he took the phenomena in question as established facts (on the basis, presumably, of his own teaching experience), without attempting to examine their frequency and extent.