This paper presents the findings of research investigating first-language attrition of Turkish speakers in Australia and the role of subjective ethnolinguistic vitality perceptions in that process. It examines the relationship between societal factors and individuals' perception of the language contact situation as reflected in their speech behaviour. For the linguistic dimension of the study, a number of lexical and syntactic tests along with self-rating scales were administered to 40 Turkish-Australians in Sydney and 40 reference-group informants in Turkey. For the social psychological dimension of the study, data were gathered by utilising the concept of ethnolinguistic vitality and its accompanying instrument, the subjective vitality questionnaire (SVQ). The SVQ data indicate low vitality perceptions among Turkish immigrants. Also, by means of a language use-choice questionnaire (LUCQ), data were elicited on language use and attitudes of the informants. The comparative results between Turkish immigrants in Sydney and Turkish speakers in Turkey indicate lexical and syntactic attrition among Turkish immigrants.