Microbial degradation represents the major removal process of hydrocarbon contaminants from soil. Understanding the factors which impact the behaviour and biodegradation of hydrocarbons in soil is fundamental for facilitating a successful bioremediation strategy. Little is known about the impact other contaminants have on hydrocarbon biodegradation, which is of particular relevance as contaminated soils often contain complex organic chemical mixtures. This thesis investigated the biodegradation of aromatic and aliphatic hydrocarbons in soils; with emphasis directed towards the impact of other contaminants (polycyclic aromatic hydrocarbons, carbon nanomaterials, cable insulating oil and weathered hydrocarbons) and enhancing biodegradation through biostimulation and bioaugmentation. The catabolic activity of indigenous soil micro flora was further found to be dependent on prior exposure to hydrocarbons, with biodegradation also found to be strongly affected by (a) hydrocarbon type and concentration microflora are exposed to and (b) exposure time, form and frequency. SOM was found to restrict the development of phenyldodecane degradative activity in soil, and indicated to have more of an inhibitory influence upon the biodegradation and bioaccessibility of aliphatic hydrocarbons. The effectiveness of biostimulation and bioaugmentation techniques to optimise biodegradation was influenced by many parameters, particularly hydrocarbon type and concentration; the presence and activity of indigenous microbes; and treatment type and application to soil. As such, the suitability of these techniques to facilitate contaminant biodegradation should be assessed on a site by site basis. Continued research in to the biodegradation of hydrocarbons is crucial for an environment as complex and heterogeneous as soil, and the ongoing development of risk assessment and bioremediation practices.