In this paper we present the results of a study of the tonal adaptation of a corpus of c. 300 Mandarin and 40 English loanwords in Lhasa Tibetan drawn from Yu et al.’s (Colloquial Lhasa Tibetan-Chinese Dictionary, 1980). Our principal finding is that no equivalence is made between the Mandarin tones/English stress contours and Lhasa Tibetan tones. Instead, tones are assigned by a combination of default rules of Tibetan grammar and UG enhancement processes familiar from the tonogenesis literature.