There is a need for empirical investigation of the optimal length for drill sentences at various states of second language learning. This paper reports the results of a study that explores the effects of sentence length and grammatical structure on the ability of foreign students to repeat English sentences. It was hypothesized that sentences of the same length but with different syntactic structures would not be equally easy to repeat. The results show that repeatability of sentences depends on the syntactic structure of the sentences, as measured by type of sentence expansion and sentence pattern, as well as on the number of words in the sentence. The results also indicate that as sentences become longer the effect of the structure becomes more pronounced. In constructing drill sentences for foreign language learners, sentence pattern, type of sentence expansion, and sentence length should all be considered of prime importance. (Author)