This thesis investigates some of the theoretical issues currently considered in the literature concerning the key determinants of opinions held by consumers regarding complex and controversial technologies, specifically related to the theories of risk, group polarization theory and Rogers' Diffusion of Innovation theory. Much of the current literature on risk falls under one of two major perspectives; the cognitive-science perspective, which views risk in terms of objective hazards which can be calculated and controlled for, and the sociocultural approach, which considers risk a socially constructed phenomenon. Group polarization theory predicts in situations which are novel or ambiguous, attitude polarization will shift over time in the direction of a valued group norm. Additionally, diffusion theory predicts attitudes regarding innovative technologies will, over time, become more positive and should move in the direction of trusted opinion leaders. The body of this thesis is made up of two journal articles examining the key determinants of consumer opinions of complex and controversial technologies. The first article examines a number of factors representing the cognitive-science and the sociocultural perspectives related to consumer opinions of biotechnology. Support was found suggesting both perspectives are important. The second article examines consumer attitude over time, deriving hypotheses from polarization theory and diffusion of innovation theory, using a different complex and controversial technology (food irradiation), and a different data set which employed a time-series design. Findings support the polarization hypothesis, and some of the diffusion hypotheses. General conclusions and suggestions for further research are discussed.