Although there are many publications, mostly from before the Revolution, on divorces in Rus and Russia, the issue of divorces in the Rurik dynasty in the Middle Ages has not been discussed separately. The present article is in fact the first attempt to present the reasons, circumstances and procedures of ducal divorces in the 12th and 13th c. In the first part the author tries to estimate the total number of divorces in the important and relatively well-documented lines of the Rurik dynasty (Mstislavovich and Vsevolodovich lines) and their share in the total number of divorces documented in the sources on the dynasty. The second part discusses nine examples of ducal divorces. On the basis of the facts connected with the breakdown of the relevant marriages the author stipulates that divorce was not uncommon in Rus at that time. For instance, out of the fifteen children of Mstislav Fyodor Vladimirovich Monomakhovich who are noted in sources, two divorced their partners, and so did two of the ten children of Vsevolod Yurievich the Big Nest. The legal options of dissolving a marriage included: sending the wife away by the husband, divorce by mutual agreement, detaining one of the spouses by a person who had authority over him/her, entering a convent by one of the spouses, divorce due to a lengthy absence and not fulfilling marital duties. There was one example of an illegal divorce forced by a third party (forcing the spouses to enter a convent). There were no cases of annulling marriages because of the spouses being too closely related, which was common in the West. The results indicate that this previously unexplored topic deserves further investigation. Researching it deepens our knowledge about the mediaeval culture of Rus and about its ducal families treated as social units.