In this work, a number of mathematical models of haptotactic cell migration are developed. These models of haptotaxis are presented in two distinct parts - the first comprises an investigation of haptotaxis in pre-necrotic avascular tumours, while the second consists of the modelling of adhesion-mediated haptotactic cell migration within tissue, with particular attention paid to the biological appropriateness of the description of cell-extracellular matrix adhesion. A model is developed that describes the effects of passive and active haptotactic migration on the cellular dynamics and growth of pre-necrotic avascular tumours. This model is also extended to describe the internalisation of labelled cells and inert microspheres within multicell tumour spheroids. Also presented is a novel model of adhesion-receptor mediated haptotactic cell migration. Specific applications of the model to tumour invasion processes are then discussed. This model includes a more biologically realistic description of cell adhesion than has been considered in previous models of cell population haptotaxis.