This paper resulted from a roundtable discussion at the 1998 CUNY Sentence Processing Conference held at Rutgers University. Jerry Fodor (Philosphy, Rutgers University) an argued there that an adequate lexical semantics had to invoke a criterion of Rever se Compositionality. Fodor gives the following definition of 'Reverse Compositionality'(RC): "Nothing belongs to the lexical entry for a lexical item except what that item contributes to the grammatical representation of its hosts" where 'host is defin ed as "any expression E ...of which E is a constituent. " Moreover, Fodor claims that invoking this criterion has broad consequences for theories of language processing and acquisition, particularly with respect to theories that attribute processing beha vior to "lexical effects. Fodor claims that "...most of what cognitive science blithely refers to as lexical effects in parsing and language learning aren't in fact mediated by information of the kind that lexical entries contain...." and "... that language acquisition delivers sh allow lexical entries consonant with reverse compositionality, and that parsing delivers correspondingly shallow lexical entries consonant with assigning tokens to their types, and that everything else will turn out to be 'performance theory' ... In this paper, I argue that frequency and other standard lexical processing effects can form a legitimate part of a theory of sentence processing even if it adopts the criterion of "reverse compositionaliy". Cases drawn from the literature are used to s ketch what a theory adopting Fodor's criterion and using frequency and/or probabalistic information would look like. This commentary will appear in Proceedings of CUNY Conference on Sentence Processing, 1998, S. Stevenson and P. Merlo, eds, J. Benjami ns.. Also cross-referenced as UMIACS-TR-98-52