Abstract: This article describes stages in annotation of the 113 million Corpus of Contemporary Serbian (preparation and implementation). There are several levels of annotation which have been conducted. Corresponding bibliographical information is attached to each corpus text. Part-of-speech (PoS) tagset is prepared, based on the electronic morphological dictionary of Serbian, as well as dictionary of possible annotations adapted for TreeTagger, the PoS tagging system. The Corpus of Contemporary Serbian has been automatically, morphosyntactically annotated with TreeTagger software, i.e. information about part of speech and lemma has been attached to each corpus word form. TreeTagger used manually tagged one million word corpus INTERA as a training set. Ten-fold cross-validation is used for evaluation of applied annotation procedure.