The objective of my thesis is to investigate Passivization in two different theories of grammar, namely Standard Theory and Lexical-Functional Grammar. In the first chapter I am going to introduce the architecture of the theories and explain the major concepts and terms within their framework. The second chapter gives an overview of the theoretical aspects of Passive formation within these theories. The most outstanding difference could be summarized as follows: in Standard Theory Passivization is a syntactic transformation applied to active Deep Structure representations, from which it derives passive Surface Structure sentences. On the other hand, LFG postulates a lexical Passive rule that is capable of reassigning particular grammatical functions of arguments, therefore in this case it is a lexical process. The third chapter offers an extensive reasoning against transformational treatment (in ST) of Passivization and demonstrates superiority of the LFG-style lexical rule of Passivization. Among the most important arguments such notions and constructions will be concerned as selectional generalization, strict subcategorization, idiom chunks, prepositional passives, double passives, raising and equi.