The philosophy of comprehensive education embedded in Scottish policy has long been recognised as an exemplary feature (Humes & Bryce, 2003). The commitment to language learning is evident in recent policy supporting primary pupils who will learn two languages as well as the language of their school (Education Scotland, 2015a; Scottish Government, 2012). For most children, this will involve English and two other languages, one of which could involve Gaelic. For children enrolled in Gaelic medium education, Gaelic is identified as the first language, coupled with English and a further modern language (Education Scotland, 2015b). Although this policy can be applauded, it may further complicate Gaelic medium education provision where the outcome is to provide pupils with an equal footing in Gaelic and English languages. The paucity of research focused on assessing and diagnosing language difficulties in Gaelic is particularly concerning. This paper approaches this need by reviewing available research and literature around this topic. A summary of policy, research and related fields is provided, including suggestions for potential future activity. This paper identifies compelling evidence that the development of support resources for children becoming bilingual through Gaelic medium education should take place as a matter of urgency.