First language and second language learners have to learn through making mistakes. Foreign language learners do not have to learn, to anything like the same extent, in this way. Foreign language teachers should study students' mistakes in order better to understand how they are learning and mislearning. Teachers should try to avoid language teaching procedures which appear likely to cause students to make mistakes. If, however, the teacher is too strict about mistakes, learners will not be bold in use of the language and their progress will be retarded. There are times for controlled and correct use of the language and times for adventurous use. Mistakes are not to be encouraged, but sometimes they should not be strongly discouraged. (Author/DB)