Bioremediation is being increasingly seen as an effective, environmentally benign treatment for shorelines contaminated as a result of marine oil spills. Despite a relatively long history of research on oil-spill bioremediation, it remains an essentially empirical technology and many of the factors that control bioremediation have yet to be adequately understood. Nutrient amendment is a widely accepted practice in oil-spill bioremediation but there is scant understanding of the systematic effects of nutrient amendment on biodegradative microbial populations or the progress of bioremediation. Recent laboratory and field research suggests that resource-ratio theory may provide a theoretical framework that explains the effects of nutrient amendment on indigenous microbial populations. In particular, the theory has been invoked to explain recent observations that nutrient levels, and their relative concentration, influence the composition of hydrocarbon-degrading microbial populations. This in turn influences the biodegradation rate of aliphatic and aromatic hydrocarbons. If such results are confirmed in the field, then it may be possible to use this theoretical framework to select bioremediation treatments that specifically encourage the rapid destruction of the most toxic components of complex pollutant mixtures.