Profiling the acquisition of a minority language is an important factor in understanding the range of abilities in typical bilingual language acquisition. When this minority language is endangered, as in the case of Irish, it becomes even more important to document how both languages are acquired, to document typical development in young children where a language is changing (O’Toole & Hickey, 2012). This should help to determine the effect of maintenance programmes and to plan for the future. Furthermore, when the issue of identifying a potential language delay or disorder is at stake, knowing what to expect in terms of typical acquisition in that language is even more critical. This paper will look at vocabulary acquisition in a group of young Irish-English bilinguals using a tool that was developed to capture early bilingual vocabulary development. Using a bilingual Irish-English adaptation of the MacArthur-Bates Communicative Development Inventories: Words and Sentences (CDI:WS) (Fenson et al., 2007), longitudinal parent report data were collected from 45 children (27 girls and 18 boys) at 4-monthly intervals, resulting in 100 data points between the ages of 17-36 months. Preliminary analysis found that according to the estimates of language exposure, the caregivers indicated that they ‘always’ spoke Irish to the children. However, closer inspection found that in the high contact situation of Irish now, both languages were, in fact, used in most households, with/among siblings and extended family. Nevertheless, the children’s vocabulary indicated that they were Irish-dominant in this age range, with more Irish words than English for all vocabulary categories. The analysis also showed no difference in Irish vocabulary scores between children who were ‘usually’ exposed to Irish compared to those with lower exposure rates to Irish. This means that a drop in reported input frequency from ‘always’ being exposed to Irish to ‘usually’ has significant implications for the amount of words in Irish that a child will be reported to know. In contrast, there was a significant effect for caregivers’ reported use of English on children’s English scores. Children who were ‘usually’ exposed to English had significantly higher English vocabulary scores than those who were ‘rarely’ or ‘never’ exposed to the language. The results are discussed in terms of the language input needed to maintain and support typical development of an endangered language and factors to take into account for establishing good estimates of language exposure in a minority language context.