In two parts, this thesis examined retronasal perception of single odours, binary odour mixtures and odour-taste mixtures. Part 1, aimed to determine if perceived retronasal temporal order differs to that order perceived via the orthonasal pathway and if retronasal temporal order is a function of an odorant’s water solubility or nasal mucus solubility slowing the odorants progression to the olfactory epithelium via the longer retronasal route. Part 1 established that retronasal temporal perception of binary odour mixtures differs from orthonasal temporal perception and that nasal mucus solubility and the “stickiness”, mediated by volatility, are the factors determining the perceived retronasal order. It was further concluded that nasal mucus and not water was the most appropriate approximation to the composition of nasopharyngeal mucus. Part 2, aimed to determine if correct retronasal odour identification is a function of learned taste-associations and if correct retronasal odour identification is a function of the modality through which the odour is learned. Part 2, established that in simple binary odour-taste mixtures correct retronasal odour identification is not a function of learned taste-associations, nor do tastants suppress odours. However, it was concluded that mouth-learning experience does provide odours with an identification advantage retronasally, over odours that are not learned through the mouth. Overall, the Thesis demonstrated that differences exist between retronasal and orthonasal perception. Specifically, the perceived temporal order of components in binary odours mixtures is determined retronasally by an odour’s nasal mucus solubility and “stickiness”. The exploration of this mechanism in future research may provide a greater understanding of temporal odour perception and the means to increase odour mixture component identification beyond the current limit of three. Furthermore, retronasal odour and taste processing seem to occur independently of each other, as learned-associations between taste and odours do not impact on the accuracy of mixture component identification or intensity. It may be that it is mouth-learning experience or a relationship to food that is important to retronasal odour perception rather than any component congruency. Future research should aim to determine if it is mouth experience or the contribution of other stimuli such as tactile cues that contribute to the increase in retronasal identification accuracy. / Doctor of Philosophy (PhD)