In the article the question are considered of normative adjusting and the practice of application of United Nations Convention on Contracts for the International Sale of Goods (the Vienna Convention) which was signed in 1980 by the economic courts. The procedure of applying the articles 74, 78 of the Convention which concern the cases of definition loss sizes are analyzed in the clause. The practice of applying article 79 of the Convention on cases concerning the absence of liability for non-fulfillment of obligations is investigated. The questions about the application of international commercial contract principles (UNIDROIT Principles) in international trade practice in totality with Vienna Convention, as a rule of international trade practice are considered.