Due to differences in the grammars of English and French, "pendant" and "depuis" are as difficult to master for English speakers as their equivalents "for" and "since" are for French speakers. To the former, three facts are crucial: (1) "depuis" corresponds to both "for" and "since," which creates ambiguities; (2) "depuis" applies to an uncompleted process, while "pendant" assumes completeness; and accordingly, (3) different verb tenses are used for "depuis" and "pendant." However, one French tense typically used for a completed process, the passe compose, looks like a literal translation of an English tense specialized in incompleteness, the present perfect. Native-language interference is likely to linger in this case, so for the teaching of this specific situation, recourse to contrastive methods seems necessary. This is a topic that the grammar-translation method was better prepared to teach than are more modern methods. (Author/MSE)