A study of advanced English learners' use or avoidance of English idioms is described. The investigation looked at whether the subjects would attempt to use English idioms in a translation task containing idioms, or would instead use non-idiomatic synonyms or paraphrase. It also looked at which idioms are used and which are avoided: those that are identical to idioms in the first language, those that are different, those that are commonly used, or those that are semantically transparent. The subjects were 12 bilingual Spanish/English speakers who had learned English as a second language as adults but whose conversation showed very few grammatical or lexical errors. The results showed that the best-known English idioms were the ones with identical Spanish equivalents, and the least known were totally different in the two languages. There was no correlation between idioms produced the most and frequency of general use. Semantic transparency appears not to be as important as similarity to a first-language idiom. The study does not measure the use of the idioms in normal conversation, cannot measure the number of idioms known or unknown, and does not distinguish between true avoidance representing choice of usage and apparent avoidance due to lack of knowledge. The relationship of avoidance and communication strategies and the study's implications for teaching idioms are also discussed. (MSE)