A case study was undertaken to examine the influence of one aspect of signed grammar, transparency of reference of some signs, on the acquisition of possessive pronouns in American Sign Language (ASL). The subject was a hearing child of deaf parents who was learning ASL and English. Data were collected in home visits betwen the ages of 1.1 and 3.2 in videotapes and anecdotal records. The Curtiss-Yamada Comprehensive Language Evaluation measure was used to assess receptive language, with stimuli translated into ASL to assess comprehension of the relevant structures in sign language. Four stages were found in the subject's mastery of possessive forms: (1) use of names to indicate possessor in both languages; (2) appearance of some possessive pronouns in both languages (first and second person, and some third person in ASL), with some names still used for reference; (3) correct production of possessives in English for first and second person forms, with continuation of stage 2 errors in ASL and with a new signing error of indicating the object rather than possessor; and (4) correct use of first and second person forms in English and ASL, with the few remaining errors in number and gender of the third person forms. Results suggest there was not an apparent advantage in learning signed grammar as opposed to spoken grammar, since the acquisition of possessives occurred simultaneously in the two languages, and signed possessives may have been more difficult. It is concluded that children probably do not take advantage of special cues to grammatical competence available to them. (MSE)