This study examined morphological skills in a girl with cri du chat syndrome, addressing three questions: (1) To what extent does the subject inflect words? (2) To what extent are words inflected correctly? (3) To what extent do the inflected words reflect productive morphological rules, and to what extent can they be considered to be rote-learned? The study draws on two sources of data: a corpus of spontaneous utterances collected when the subject was 14 years old and her performance on a past tense elicitation test at 11;10 and 16;5. It was found that most inflectional forms in the nominal, verbal, pronominal and adjectival paradigms of the target language were attested in the corpus. These forms were in all but a few instances inflected correctly. The most frequent inflection errors were infinitive for present, past or past participle in verbs and wrong gender in determiners. Furthermore, performance on the elicitation test indicated some knowledge of productive inflectional rules of the target language, despite relatively poor phonetic, phonological and syntactic skills. (Contains 9 notes and 14 tables.)