Metadiscourse markers are universal aspects of our everyday language and major features of the way we communicate in a range of genres and settings which help writers make coherent and reader-friendly texts. Despite the importance of metadiscourse in composition, reading, rhetoric and text structure and being investigated from different angles recently, it is still unknown to many writers of scientific and academic texts, teachers of English as a second language, translators, editors and those who are involved in the field of linguistics. This book compares and contrasts interactive and interactional metadiscourse markers in English medical texts and their Persian translation based on Hyland’s (2005) model. A corpus of 140 paragraphs of English medical articles and their translation into Persian, published in Sina Journal, were selected and the frequency and types of metadiscourse markers were analyzed in each text using the paired t-test and Wilcoxon signed-rank test. The results showed that there is a statistically significant difference in the amount and types of metadiscourse markers in English medical texts and their Persian translation.