Annelids are becoming more and more popular model to study regeneration, as, being highly organized animals, they can restore the whole body from a single segment and different annelids possess variable regenerative capacities. Despite a large amount of works on polychaetes regeneration we are far from understanding why some animals can easily growth out both body ends and some can hardly heal the injury. Our project is devoted to the reading, assembly and analysis of trascriptomes of two polychaetes Platynereis dumerilii (Nereididae, Annelida) and Pygospio elegans (Spionidae, Annelida) at different stages of their regeneration. P.dumerilii is only capable of caudal regeneration, while P.elegans can quickly restore both the head and the tail body parts in case of loss. We consider it to be of great interest to compare the gene sets that are activated at different timepoints at the head and tail regeneration sites. We hope that in the case of success our data will help to answer a number of questions, i.e. (i) which genes are activated at the head and tail cut sites at different timepoints of regeneration process of two polychaetes that varies in their regenerative capacities (ii) which conservative regulatory genes are involved in polychaete regeneration (iii) which genes demonstrate the differential expression in the areas of anterior and posterior regeneration (iv) why P. dumerilii lacks the anterior regeneration.