The main goal of this dissertation is to develop simple and accurate models for thetransient monotonic and cyclic deformation behaviour of bitumen and asphalt mixes. The first part of this dissertation is concerned with an experimental and theoreticalinvestigation of the deformation behaviour of bitumen. The second part is concernedwith the deformation of bituminous mixes. A brief description of the main literature on composition, structure and mechanicalbehaviour of pure and polymer-modified bitumens is presented in chapter 2.An extensive experimental study comprising of monotonic, continuous cyclic andpulse loading tensile experiments for two pure and two polymer-modified bitumensis detailed in chapter 3. Based on these experimental findings a simple constitutivephenomenological model including the effects of rate dependent recovery is proposedfor bitumen. Comparisons between experiments and model predictions are presentedwith good agreement. The spherical indentation behaviour of bitumen under monotonic and cyclic loadingconditions is studied in chapter 4. A simple extension to the power-law indentationmodel of Bower et al. (1993) is proposed for bitumen with good agreement withexperimental results. Chapter 5 presents a review of the main research on continuum and micro-mechanicalmodels for the deformation behaviour of bituminous mixes. An extensive experimental investigation of the monotonic and cyclic compressivedeformation behaviour of bituminous mixes with varying volume fractions of aggregate,for uniaxial and triaxial conditions, is described in chapters 6 and 7, respectively. An extension to the phenomenological model proposed for bitumen is proposed forthese mixes. The predictions of the model are compared with the experimental resultswith good agreement. In chapter 8, a micro-mechanical constitutive model for the deformation behaviourof asphalt is assembled using micro-mechanical theories and experimental observations. The model predictions are compared with uniaxial and triaxial experimentalresults, showing reasonably good agreement. Finally, conclusions and recommendations for future work are presented in chapter 9.