The preparation of polymeric derivatives of drugs, in which drug moieties are covalently linked to polymeric or oligomeric matrices, in such a way that they can be released at the site of action, is one of the most promising ways to achieve results which often can be hardly obtained by other means, such as, for instance, better adsorption by some ways of administration (e.g., oral administration), preferential localization in the body, and longer duration of activity. The aim of this review is to provide an up-to-date picture of the state of art in this field. The synthetic aspects of the preparation of polymeric derivatives of drugs will be discussed, with special emphasis on general methods. The main criteria for selecting a particular type of matrix, and a particular bond between drug and matrix, in order to achieve a given purpose, will be also discussed. The main pharmacological results so far obtained by this technique will be emphasized.