ENIt is noted that Krevsk union is of global importance in the history of the statehood of Belarus, it ushered in a new stage in the development of public relations of the Grand Duchy of Lithuania and Poland – stage personal dynastyk union, which lasted until the Union of Lublin in 1569. The political and legal analysis Krevsk Union is given, the causes and consequences of its conclusion are examined. The assessment of Belarusian, Polish and Lithuanian researchers of the legal status of the Grand Duke of union conditions are analyzed. two possible vector historical development Grand Duchy Lithuania are considered – southwest (Union Poland), and northeast (union with Moscow) shown circumstances selection Yahajlo Western vector development Principality. Crusaders shown inconsistency alleged religious motives of their trips to Lithuania. It is noted that Krevsk union objective was beneficial not only to the Grand Duchy of Lithuania and Poland, but also the peoples of Eastern Europe, as the united force against the Crusaders aggression contributed to the development of production and trade ties between the states. However, the union also had a negative effect on the Grand Duchy, as promoted the expansion of the Polish feudal lords on his land, forcibly stick a catholic faith of the population. Keywords: Krevo union, the Kingdom of Poland, Grand Duchy of Lithuania, Grand Duke of Lithuania, King of Poland, Orthodox Christianity, Catholicism, the Crusaders, the development of vectors.