It is well known that adult US-English-speaking learners of French experience difficulties acquiring high /y/-/u/ and mid /oe/-/[openo]/ front vs. back rounded vowel contrasts in French. This study examines the acquisition of these French vowel contrasts at two levels: phonetic categorization and lexical representations. An ABX categorization task (for details, see Section IV) revealed that both advanced and intermediate learners categorized /oe/ vs. /[openo]/ and /y/ vs. /u/ differently from native speakers of French, although performance on the /y/-/u/ contrast was more accurate than on the /oe/-/[openo]/ contrast in all contexts. On a lexical decision task with repetition priming, advanced learners and native speakers produced no (spurious) response time (RT) facilitations for /y/-/u/ and /oe/-/[openo]/ minimal pairs; however, in intermediate learners, the decision for a word containing /y/ was speeded by hearing an otherwise identical word containing /u/ (and vice versa), suggesting that /u/ and /y/ are not distinguished in lexical representations. Thus, while it appears that advanced learners encoded the /y/-/u/ and /oe/-/[openo]/ contrasts in the phonological representations of lexical items, they gained no significant benefit on the categorization task. This dissociation between phonological representations and phonetic categorization challenges common assumptions about their relationship and supports a novel approach we label "direct mapping from acoustics to phonology" (DMAP). (Contains 5 tables, 5 figures and 1 note.)