The inverse resolution(IR for short) is a procedure to produce new clauses by applying the resolution principle in the opposite direction. It has mainly been studied in terms of logic. The elementary formal systems(EFSs for short) invented by Smullyan have been proved suitable for formal language learning as a uni ed framework. In this paper we consider the problem of learning EFS languages from positive examples by applying IR in EFS framework. First, we give a realization of IR in EFS. Based on the realization, we try to give an e cient learning procedure for an EFS language class, which is a subclass of regular languages, from positive examples.