The high level of investigative activity to date into information systems and information technology acceptance and diffusion has witnessed the use of a wide range of exploratory techniques, examining many different systems and technologies in countless different contexts and geographical locations. The aim of this paper is to provide a comprehensive and systematic review of the literature pertaining to such adoption and diffusion issues in order to observe trends, ascertain the current ‘state of play’, and to highlight promising lines of inquiry including those lacking investigative activity or simply being in need of renewed interest. Previous research activity was analysed along a number dimensions including units of analysis, research paradigms, methodologies, and methods, theories and theoretical constructs, and technologies/contexts examined. Information on these and other variables was extracted during an examination of 345 papers on innovation adoption, acceptance and diffusion appearing in 19 peer-reviewed journals between 1985 and 2007. Findings suggest that the positivist paradigm, empirical and quantitative research, the survey method and Technology Acceptance Model theory (and its associated constructs) were predominantly used in the body of work examined, revealing clear opportunities for researchers to make original contributions by making greater use of the theoretical and methodological variety available to them, and consequently reducing the risk of research in the area moving toward overall homogeneity.