A major obstacle to the early diagnosis of language shift is the absence of an easy-to-use measure of language strength. The body-part naming task being developed as part of the Hawai‘i Assessment of Language Access (HALA) project exploits the fact that the speed with which bilingual speakers access lexical items in their two languages offers a sensitive measure of relative language strength. It also allows the evaluation of label accuracy, another indicator of language strength. The purposes of this study are to (i) further assess the HALA approach, (ii) assess Truku strength (vs. Mandarin) across age groups, and (iii) establish baseline data as a starting point for developing conservation programs.A total of sixty-eight participants in four age cohorts were tested (ages: 10–15, 16–25, 26–40, and 41–65). All were ethnic Truku. As predicted, Truku (non-dominant language) produced longer response times and lower accuracy than Mandarin (dominant language) across all speakers suggesting a cross-generational decline of Truku. Moreover, response time offers a more precise and superior measure of language access than accuracy does. Young adults and youth score equally well on vocabulary access in Truku, but the youth have slower response times―suggesting further decline and the need for urgent remedial action if Truku is to survive for another generation.