The imidazole dipeptides (ImD); anserine (Ans), carnosine (Cam) and balenine, have been shown to be effective at functioning as H+ ion buffers, with Carn being particularly effective within the physiological pH range. Therefore ImD have been reported to be beneficial to athletes exercising at high intensities, where the activity results in the production and accumulation of H+ ions within skeletal muscle. It has also been hypothesised that these compounds may also be beneficial in reducing the morbidities related to ageing, such as Alzheimer's disease. Humans store ImD in the form of Carn and not as anserine or balenine. However, within the human body Carn production is limited by the ability to degrade uracil in the liver, with (3-alanine being the limiting factor. Therefore the content of the diet has a substantial impact on the level of Carn within human skeletal muscle. This thesis aimed to investigate the variability in ImD with age and in subjects from different geographical locations. The effect of ageing on the muscle content of the ImD was demonstrated through the use of a murine model, where increased age was accompanied with a 45% decline in the ImD levels measured in the tibialis anterior of 60wk old senescence-accelerated male mice (Chapter 9). This is supported by further work (Chapter 14) which showed that elderly European subjects exhibited lower levels of carnosine in the vastus lateralis compared to younger European subjects (15.6mmol·kg-1 dm and 22.4mmol·kg-1 dm respectively). However, in Korean elderly subjects no decline was observed (21.5mmol·kg-1 dm), and this could potentially be explained by different dietary habits, with the elderly Korean subjects consuming larger amounts of protein-rich foods than their European counterparts. Analysis was made of the variation in the carnosine content of the vastus lateralis in subjects from differing geographical locations, and subsequently different cultural diets with varying meat contents, and showed that dietary intake of a diet habitually rich in the ImD could potentially 'over-ride' the decline seen with age in subjects who 'reduce' their meat intake.