This chapter will deal with the problems involved in the investigation of language loss (or language “attrition” as it is often called: see Lambert and Freed, 1982) with special reference to “crosslinguistic influence” (CLI). CLI is a term adopted in an earlier paper on language loss (Sharwood Smith, 1983a) and discussed fully in Sharwood Smith and Kellerman (1986). It is a psycholinguistic term referring to the influence on the learner which one language system he or she possesses may have on another language system. This is irrespective of whether the language system is a mature language or whether it is in a developmental stage or fossilized before attaining maturity. The term is meant to cover more than the word “transfer” and includes borrowings, influence on L1 from L2, avoidance of transfer, etc. In other words, it covers a fairly wide range of phenomena (see Sharwood Smith and Kellerman, 1986). As far as CLI in an attrition context is concerned, the attraction of language loss studies for the present writer dates from about the time when he supervised a Utrecht-based project carried out by Galbraith and Van Vlerken on adverbial placement amongst young native-speakers of English resident in the Netherlands, which showed how language loss was not simply confined to situations where the language under “attack” was a low-prestige language and/or where native-speaker input was no longer available to the speaker (see Van Vlerken, 1980; Galbraith, 1981; Sharwood Smith, 1983a, 1983b).