In the present investigation, 15 first term university students were faced with 80context-based idioms in English (L2) and Swedish (L1) respectively, 30 of whichwere in the source domain of animals, commonly used in both languages, andasked to explain their meaning. The idioms were of varying frequency andtransparency. Three main research questions were thus addressed:1. How well do students master idioms in their L2 as compared to their L1?2. How do (a) degrees of transparency, (b) idiom frequency and (c) thechoice of source domain affect students’ L1 and L2 comprehension?3. To what extent is context used when interpreting L1 and L2 idioms?Results show that while the frequency of an idiom does not appear to play apart in whether it is comprehended or not in either language, the degree oftransparency is of great importance in students’ L2. Also, students make extensiveuse of context in their L2.