1 Abstract— This Paper aims to review IT adoption literature concerning validation and development of Unified Theory of Acceptance and Use of Technology (UTAUT). In [1] UTAUT was introduced as an accumulation of various research efforts represented in different models and theories of Technology Acceptance. The UTAUT is considered as a trial to unify terminology of variables of different models and theories of Technology Acceptance. The theory was established on four theoretical constructs representing determinants of Use Behavior or the Intention to Use, which play essential roles as surrogates of Technology Acceptance. These constructs are: Performance Expectancy, Effort Expectancy, Social Influence, and Facilitating Conditions. In addition to these variables the theory considers also Moderating Factors which moderate the relations between various constructs and Intention to Use. The Moderators are Gender, Age, Experience, and Voluntariness of use. It has been a decade since UTAUT was first introduced by [1]. Since then numerous studies either empirically validate or theoretically contribute to the theory. Some of them empirically validate the theory (either in western countries or across different cultures) or even replicate results of [1]. Theory validation and adaptation to be applied in different settings are briefly discussed. A literature review revealed three major trends of theoretical contributions to the theory: suggestion of New Constructs, suggestion of new Moderating Factors, and Finally Theory Extensions and Integration with other theories and models. These research trends are addressed in this Paper. Index Terms—UTAUT, Technology Acceptance, IT adoption, Performance Expectancy, Effort Expectancy, Social Influence, and Facilitating Conditions. I. INTRODUCTION hile organizations sought to meet the growing needs of information, especially in the modern business environment which is characterized by risk and uncertainty, they adopt information technology to enable them to meet their information needs. It has been well established, in IT adoption literature, that IT won't be effective unless it is used. Since the seventies of twentieth century, researchers search for and In proceedings of Fourth International Conference on ICT in our lives 2014 ―Information Systems Supporting Decision Making” (ISSN 2314-8942), Information Systems and Computer Science Department, Faculty of Commerce, Alexandria University, Alexandria, Egypt, December 20-22, 2014. determine factors that contribute to enhancement of integration of information systems with operations within organizations. These research efforts resulted in a great number of factors. Among these factors system use gains researchers interest [2]. As shown in [3], current research efforts regarding System use results in two main research streams; User Satisfaction and Technology Acceptance. At the beginning, researchers’ attention was drawn to User Satisfaction which is defined as "the sum of one’s feelings or attitudes toward a variety of factors affecting the situation" [2] pp. 192. On the other hand, based on general assumption that the relationship between the use of information technology and the performance is positive, it was pointed out in [4] that researchers examined many factors ( related to individuals, organization , and technology ) to specifying main factors that affect system use behavior . These efforts result in Technology Acceptance as surrogate of system use. Researchers in IS field proposed models, which are derived from Social psychology field, concern with Behavioral Intention as a possible theoretical foundation for system use determinants [5]. Technology Acceptance Models tried to identify and investigate Behavioral Intensions of users. As a matter of fact, there is a variety of Technology Acceptance models and theories. Although they are similar in concepts and variables, they differ in methodologies and interpretation of the phenomenon (Technology Acceptance). Unified Theory of Acceptance and Use of Technology (UTAUT) was introduced by [1] as an accumulation of various research efforts represented in different models and theories of Technology Acceptance. The UTAUT is considered as a trial to unify terminology of variables of different models and theories of Technology Acceptance. Development of this theory has many facets. These are addressed in this paper. This paper is organized as follows. Section II represents theoretical foundation of UTAUT. Section III reviews IT literature adoption for UTAUT Validation. Section IV represents the first facet of UTAUT development, New Constructs. Section V represents the second facet of UTAUT development, New Moderators. Section VI represents the final facet of UTAUT development, Model Extensions and Integration with other Models. Finally, Section VII shows Conclusions. Unified Theory of Acceptance and Use of Technology (UTAUT) A Decade of Validation and Development Mohammad I. Ahmad M.S., MAIS Alexandria Univ., Egypt, PGD IT, Amity Univ. India. mohammad.ibraheem.ahmad@gmail.com W