This paper proposes various strategies for the checking of integrity constraints in multidatabase systems which support nested transactions. The solution presented in [8] for centralized environments is extended. The principle of this solution consists of designating a subtransaction which controls the checking of each integrity constraint. This sub-transaction is the smallest common ancestor (within the nested transaction tree) of all the sub-transactions which might violate the constraint. In the case of a multidatabase, it is necessary to take into account the constraint structure and the localization of the sub-transactions, to choose the site where the checking should be performed in order to minimize data transfers through the network. For this purpose, different checking strategies are presented depending on the type of the constraint to be checked.